ARTICLES ON CLOCKMAKING

AND REPAIR

by John C. Losch

John C. Losch & Co., Clockmakers

Holliston, Massachusetts

All articles below are copyrighted by John C. Losch. They may not be published or sold wholly or in part without written permission of the author. Quotations from these articles must be attributed to the author.

Metal Finishing Articles:

Clock Cleaning Solution
Filling Engraved Dials (Waxing)
Lacquering Dials
Lacquering Brass
Applying Shellac to Metal
Golden Lacquer Finish
Spotting Chronometer and Clock Plates

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Shop, Bench and Tools:

Bench and Shop Layout
Adjusting Cone Bearing Lathes
Replating a Watchmaker's Lathe
Choosing a Bushing Tool
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Clockmaking and Repair Procedures:

Pivot Polishing Techniques
Why Pallets, Pivots, and Bearings Wear
Some Thoughts on Adjusting Deadbeat Pallets
Some Thoughts on Choosing and Using Clock Oil

December 16, 1997

The following materials are needed to fill engraved dials. Black sealing wax is the preferred filling material, despite occasional references to "enamel." Sealing wax is made and available from large office supply houses, and it is sold as filling material for use by cabinetmakers. It is a mixture of hard wax and shellac. A rubber squeegee such as used for the application of "body filler" (Bondo) can be obtained from automotive suppliers for pushing melted wax into the engraving. An electro-typer's 2" by 3" rubber block is used to grind and level the wax. In addition, a source of localized heat is needed such as a Bunsen burner, a propane torch, or a similar source of controlled flame. A gas ring, or electric stove burner is not suitable. Flour of pumice sometimes found in hardware stores and available from dental supply houses will be needed to level the wax after the engraving is filled.

Normally, unless damage to the wax used to fill engraving is minimal, it is best to remove the old wax, then refill the entire dial. Old wax becomes brittle, and wax which has cracking and is falling out of the engraving can rarely be made to flow evenly when heated to try to rejuvenate it. The oils in old wax harden, and the wax shrinks so that it needs to be supplemented, if not replaced. The effect of mixing old and new is uneven and unattractive in appearance.

To remove old wax, it is best dissolved out of the engraving at the same time the old lacquer or shellac used to seal a silvered or brass dial is removed. Most water-based clock cleaning solutions will accomplish both jobs, especially if the dial is first wiped with a paper towel moistened thoroughly with acetone. A soak in detergent will work too, but there is a risk of pitting the brass dial if it is left in detergent too long. Real soap, such as Ivory flakes, will work more safely. Once the old wax has softened sufficiently, it can be flushed away with hot water and a bristle brush of moderate stiffness. A tooth brush works well.

There is no need to be concerned about residual silver since the process of applying and preparing new wax will, as a side effect, wear away any remaining silver. New wax needs to be melted into the engraving. Begin by heating one numeral and the surrounding engraving with application of heat behind the area to be filled (12 is the logical starting point). Lightly rub the stick of sealing wax around the engraving, being careful that the heat is sufficient to melt the wax to liquid, but not enough to make the melted wax boil.

As soon as the area being heated is filled, scrape the excess melted wax toward the next numeral using the "body" squeegee. Transfer the heat to the area where the wax is being pushed, and add more wax if needed to fill the new area. Repeat this process until all the engraved areas are filled, being careful not to neglect the chapter ring and other small areas of engraving. The squeegee process often involves moving the squeegee in different directions to assure wax is pushed into all the engraving at the same time surplus is removed from the surface of the dial.

There are rare occasions where the silver on a dial is still intact, or so nearly perfect that it can be salvaged with minor doctoring. Application of silver is an extensive subject itself, but if a salvageable condition exists, it may be possible to finish the waxing process by use of a piece of soft cotton cloth, such as the material used in tee-shirts, tightly stapled to a piece of flat wood, and dampened with denatured alcohol. Staples are used in the back of the wood, obviously. This washing process is tedious, must be done a little at a time so as not to dissolve the filling in the shallow parts of the engraving, and the wiping pad needs to be rinsed frequently since it will fill with wax.

The most common method of "leveling" the wax is to gradually and gently abrade it with a slurry of pumice and water-rubbed with the elecro-typer's rubber block. A piece of soft wood can be substituted if necessary. Early antique dials were not grained with a circular effect. That came in the nineteenth and twentieth centuries, as a general rule. Normally a random scouring pattern, applied without much pressure will leave a surface appropriate for the application of silver. Silver applied to a clean dial tends to reduce the appearance of the scouring pattern and the surface will have a neutral appearance under most circumstances.

Where a circular finish is required, it is still best to level the sealing wax in the engraving by the above method since this has less tendency to erode the edges of the engraving. In addition, there is less metal removed from the dial to reduce the depth of the engraving if the circular pattern is applied after the wax is level.

The actual graining can be done with a lathe when one is available, or a fixture can be rigged where the dial is held under a concentrically-placed and pivoted piece of wood. A portion of 400-grit wet-or-dry emery paper is tacked to the piece of wood so that when the wood is pulled over the dial and around its center pivot, a grain is imparted to the dial surface. Use the lightest pressure possible for as short a time as possible. It is important not to dig into the dial surface thus weakening the sharp edges of the engraved parts of the dial.

After the dial is ready to be silvered, every effort must be made to not touch the metal with bare hands. Any oils or other contaminants which get on the metal will cause shadows or even places where the silver fails to attach to the dial. The wax filling can be made to be a little glossy by applying gentle heat to the dial before silver is put on. This can be done in a 300-degree oven, although it is not really necessary if the dial is to be lacquered, since the lacquer imparts a glossy surface to the wax itself.

There are numerous text that describe the application of silvering compound (silver chloride) after the dial has been prepared. Jcl

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Lacquering Dials

Since early alchemists discovered how to make silver nitrate, convert it to silver chloride, and to precipitate it onto "base" metal, artisans have mechanically plated decorative pieces. They did it both for effect, and to give the appearance that a dial, piece of jewelry, flatware, tea urn, etc., was other than it really was. Silvering was adopted as yet another means of coloring metal for purposes of decoration and expression. The practice became so wide-spread that it was acceptable, became an art form, and enjoyed the same approval as veneer on wood.

Until modern times, when such techniques as vacuum metalizing allowed technicians to make "gold" bottle caps out of plastic, metal coloring was dominated by methods of oxidizing, or preventing oxidization of surfaces through combination with various chemicals or compounds. The plot thickens when we contemplate electro-plating, widely used after 1860.

While all of the above oversimplifies the history of metal coloring, one fact remains constant. Where unwanted oxidization, usually recognized as tarnish, could occur, craftsmen sought and devised ways to protect their products from the most recognizable source of tarnish: air. Thus they coated their work. Normally, I am willing to bet, a workman produced something looking a certain way with the hope that it could be kept looking that way. I do.

Through the limited sources of information I have seen, I know of several basic coatings used by craftsmen. They included wiping surfaces with animal fat and, particularly in Mediterranean areas, vegetable oil in the form of olive oil. Both of these substances harden eventually, and produce a kind of varnish. As technology evolved, resins were derived which offered more lasting protection. By the middle ages, when wood finishing by more methods than oil finishing developed, compounds leading to shellac evolved. Shellac became the metal finisher's coating of choice even into this century.

The Germans developed nitrocellulose lacquer in the last half of the nineteenth century. Eventually it replaced shellac, particularly in industry. That does not mean, however, that shellac is not still a good finish for both wood and metal in certain circumstances. I still use it, especially as a restoration procedure on both wood and metal, where authenticity is a consideration.

Getting back to silvering dials, if I have not lost you with the history lesson, silvered dials ought to be lacquered. Silver will tarnish in the presence of a hard boiled egg, given the opportunity. It will definitely tarnish in the polluted slurry we inhale as air. In the face of those observations, I will tell you how I treat silvered dials.

After I have prepared, filled and silvered the subject dial, I dry it thoroughly with compressed air, then I give it time to "adjust" to room temperature. Incidentally, I try to avoid doing dials in humid weather. Next, on critical jobs especially, I wipe the dial gently with a clean soft cloth into which I have shaken very fine chalk, (five micron marble dust), in order to abrade off any residual film which might remain from the rinsing process which is a part of silvering. I remove the chalk with a blast of low pressure compressed air, about thirty pounds, so there will be no rapid cooling and condensation.

Now I am ready to spray the dial, and what I spray on it becomes the critical concern. I still use nitrocellulose lacquer. I obtain it from the Sherwin Williams Company where it is marketed as OPEX CLEAR LACQUER T82-C12. There are probably other equal (not comparable) products on the market, but I am not aware of them. Over thirty five years ago I bought the same product, with the same label, and I thinned it almost four to one for lacquering all clock parts. I paid eight dollars a gallon for it. Now, I pay over forty dollars a gallon, and I thin it less than one to one, or fifty-fifty. Safe to say, the product is being phased out, and I will have to find an alternative.

Until the replacement compound and procedure is discovered, I will continue as follows. To prepare the lacquer, under current conditions, measure equal parts lacquer and thinner into a container, then add 10% of lacquer retarder. Thinners and retarders for acrylic lacquer will work. Thus, for example, to one quart of lacquer and thinner (16 oz. each) add a generous 3 oz. of retarder. Use a larger than one quart container, or do your own arithmetic. Shake all of this together and give it ten or fifteen minutes to go into solution. Thinner and retarder can be bought from auto parts and body shop suppliers.

I have to say all of this is arbitrary instruction, and it is subject to variation based on experience. Arrogant as it seems for me to say it, these are general rules, and they should be varied and adjusted according to conditions and experience. It would take pages to delineate every variable. Experiment to learn.

Next comes the question of how to apply the lacquer to a silvered dial. I spray it. I apply one, two, and sometimes three coats to a dial. Years ago I made a sprayer from a throat spray. It is operated by use of a "chuck" from a dentist's office. My sprayer is essentially something between an air brush and an ordinary spray gun. The fact is, either of those extremes will work.

With an air brush, the system must be used for maximum volume of compound: lacquer. The ordinary spray gun must be adjusted for large volume of lacquer at the lowest volume of air before the gun spits or drips. Normally, apply the lacquer by triggering the sprayer on and off while making passes. Starting at the bottom, with the gun spraying at about a 20 degree angle off vertical, go from left to right, move the gun to cover the next width of its pattern of spray and go right to left, etc. On, spray, off, move up. On, spray, off, move up. It becomes a rhythm. Sorry, folks, but at some point I have to cop out: practice and experience become the final teacher. (And I am still learning.)

Someone in our group brought up the question of how to prevent dissolution and flow of the filler used in the engraved parts of the dial. With spraying this is usually not a problem unless the first of two or three coats of lacquer is too thin a compound or is applied to thickly. Especially the first coat should be applied thinly, not too thin or watery a substance, and it should be allowed to dry a long time: an hour or so, so that it becomes a barrier to subsequent coats of lacquer.

Acetone, or variants of it, which are the basis of lacquer thinner, is a fairly universal solvent. It will dissolve paint, shellac ( the main ingredient of most dial filling compounds,) varnish, many plastics, and a long list of other substances. Thus, if lacquer applied over dial filler is not too wet, it will soften the filler, but not enough to make it try to go into solution with the lacquer coating to produce the undesirable feathered effect sometimes seen on lacquered dials.

Lacquer should be thin enough to prevent "orange peel" from the air used to spray it. It should be thick enough so that it doesn't run or flow into a mass or "sag" on a reasonably level horizontal surface. Dials, and other parts being sprayed for finish should be rested on stands or paper so that they are as close to level as possible. This allows for the easiest kind of lacquer (or paint) spraying. One cannot tip a car to spray it, but that is another subject entirely.

The more retarder used in the lacquer, the slower it will dry, but the more it will gloss. Less retarder: faster drying with less gloss. Sometimes the most desirable finish comes from a flat to dull surface. After the bulk of lacquer has been applied, this effect can be achieved by using excessive amounts of air and indirect spraying of lacquer so that a mist or "overspray" dulls a nearly dry glossy surface. There are other "tricks" to spraying, many of which I am ignorant.

Lacquer can be applied with a soft brush. Commercially sold brushing lacquer is generally the same lacquer being sprayed, but with more retarder to slow drying long enough for brush marks to flow out. For brushing on dials, with filler especially, it is probably wise to reduce the amount of thinner somewhat, and increase the amount of retarder. This gives the compound less tendency to dissolve the shellac filler before it begins to harden, but still leaves opportunity for the brush marks to flow away and blend as the lacquer hardens.

There are many variables to this subject which could be brought to bear, including substitutes for nitro-cellulose lacquer. I will leave those matters for a later discussion, or better, from those with more modern or different experience than mine. Lengthy as this text is, it should not scare anyone away from trying to lacquer dials in particular, or metal in general. I will say that I consider protective coating one of the most important operations performed in my shop. Good luck!

John C. Losch (October 17, 1995)

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Lacquering Brass

If you contemplate a lot of lacquering, you would do well to buy a quart (if available) or a gallon of "uncut" metal lacquer for spraying. You can reduce it with lacquer thinner, then add about 10% of retarder to make brushing lacquer. You would need to thin the lacquer to a watery consistency for dipping, and I would use little, if any, retarder for that purpose. All of these combinations of thinner, retarder, and lacquer are based on experience and have to be adjusted for specific conditions. Since nitro-cellulose lacquer is increasingly hard to find in any form, you may have to use acrylic lacquer. I am unaware of any real problems resulting from its use, and I am told it is generally applied the same way as nitro-c. I have no objection to the use of spray bombs except their cost in a high volume operation. Because I use so much lacquer, it is more economical for me to use and maintain sp ray equipment. The cost is obviated to some extent by the fact I have compressed air in use for many purposes throughout my shop. As to dipping plates, I would advise against it mainly because there is so much work involved in preparing a plate for submersion, or in removing unwanted lacquer in bearing holes, screw holes, etc., after dipping. A variety of parts may be safely dipped in thin lacquer, but some will require secondary efforts to remove unwanted lacquer. Wheels, for example, can be dipp ed if care is taken not to submerge the pinion, and pivots will have to be cleaned after dipping. The Connecticut clock factories dipped brass parts, but this was done before wheels were rivetted to arbors, plates and bridges were drilled or broache d, dials and glass were attached to dial pans and bezels, etc. I suspect British and European manufacturers followed similar procedures in production of "rolled brass" movements. Manufacturers such as Howard also lacquered plates and other parts, but un til late in their history, lacquer was applied with a brush. Much later, selective spraying and dipping were adopted.

I spray nearly all the brass on rolled brass movements. I do it immediately after cleaning and polishing of the parts. I then pr oceed to polish the pivots, thereby removing any lacquer on them. I examine lantern pinions and remove lacquer as necessary with a pipe cleaner and acetone. When I repair the movement I peg bearing holes, dipping the pegwood in acetone if there is an ac c umulation of lacquer there. I put "gun patches," soft 3" squares of flannel sold for cleaning gun barrels, under the plates when I ream for bushings. Only when dramatic repairs are required do I wait to lacquer the involved parts until the work is done.

There is a reason for this beyond cosmetic value. I lacquer for the same reasons it was done in the factories. First, I am able to work without concern for the effects of handling unprotected brass. I don't have to wear gloves to avoid fingerprints. And I don't like to see finger prints on clock movements. The second reason: old, oxidized brass has a somewhat dull surface, particularly around pivot holes, which invites migration of oil. By lacquering, there stands a better chance the oil wil l form a meniscus around the pivot, the arbor shoulder, and in the oil sink, when lacquer is present. Thus the clock stays oiled longer. All of this advice has to be tempered with historic knowledge and good judgement. I lacquer the plates of grandf ather movements and French clocks even though neither were usually lacquered originally. I don't lacquer their trainwheels, but I lacquer winding drums and French barrels. I don't lacquer the plates of marine chronometers. I do polish the plates and the oil sinks to a mirror finish. I lacquer factory made clocks because factories lacquered them. Nearly all lacquer is applied with the spray gun described in my comments on dial lacquering. As much as possible, parts are arrayed flat for spraying, or, as indicated, hung on wires. On some high-grade movements which will be displayed, I lacquer train wheels, and in many such instances I use a brush in order to assure that I don't apply lacquer where it is not wanted. The small amount of lacquer whic h finds its way to the working surfaces of wheel teeth will generally "burnish" off the faces if the train is allowed to run free for a minute or so. I, like the factory engineers before me, have never found residual lacquer there to be a source of trouble in gear trains. There is considerably more to be said about the use and application of lacquer, the length of this reply notwithstanding. This should be sufficient for now.

John C. Losch (May 31, 1996)

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Applying Shellac to Metal

I can report on my experience using shellac, but I don't have scientific answers to your questions. I do not know what is the process, but white, or clear shellac is bleached and refined more than orange shellac so that it has a more neutral appearance than orange shellac on either wood or metal. Much of my knowledge of shellac comes from a late friend who was a highly skilled cabinetmaker. He always dissolved flake orange shellac, which he usually applied with a rag. He never prepared more shellac than he expected to use in a few days. He was also VERY particular that the alcohol he used was fresh.

Both he and I have always used "denatured" alcohol bought in small quantities because alcohol draws water right out of the atmosphere. I have to confess that I don't know the difference between ethanol and methanol; the "denatured" product I use specifies that it is ethyl alcohol. Another can says it contains both. Shellac is adversely effected by water. Once moisture gets into the solution as it will over time, shellac should be discarded. That may be the reason you are getting clouding. Otherwise, I would guess there is some foreign substance in the shellac flakes, possibly from inadequate preparation. The worse aspect of moisture in shellac is that it will almost never dry. I have a clock of my own which I refinished with old shellac. It took over a year for the finish to really harden. Good shellac can be sanded within half an hour of application!

For metal, I actually buy very small quantities of prepared white shellac, rather than dissolving it myself. It is usually sold as "three pound cut," meaning it was made from three pounds of shellac to one gallon of alcohol. It should be thinned a little more. This too is a sign of the times since prepared shellac used to be sold as four pound cut.

Normally I apply shellac to metal by spraying. It can as easily be applied with a soft "lacquer" brush, and probably with one of those disposable sponge brushes. I have never tried one. Where I use it on metal, I generally apply two thin coats by spray, or one only, somewhat thicker, by brush. There will be slight brush marks, and I allow them deliberately, in order to produce the same effect found on old shellac to metal finishes.

Some cylindrical pieces are best shellacked by allowing them to revolve slowly in a back-geared lathe. This way a heavy application of thin shellac can run around the metal so that brush marks flow out but the substance does not sag or collect at the bottom of the piece as it is drying. (Same for lacquer.)

I do not heat the metal first. That would make shellac (or lacquer) dry too quickly. I apply it at room temperature. After it is dry to touch, the coated pieces can be warmed to accelerate complete hardening, but shellac reacts unfavorably to too much heat.

I have restored several early scientific instruments which had to be refinished because they had been handled in spots so that the original shellac was worn through. Surrounding the worn areas were sections with the original finish in tact, and the graining or other finish on the metal beneath looked perfect. When the old shellac was removed, the metal beneath was actually frosted or etched. I have always presumed that some of the early shellacs were impure, and there may have been acid present which activated from time to time, under humid conditions. A guess on my part.

Shellac will not gloss quite as much as retarded lacquer, but the difference is slight, in my experience. When applied to wood, shellac, lacquer, and varnish are all usually sanded between coats, then the last coat can be rubbed to a polish. I am not aware that these procedures are used for clear metal coating. I have never found the need.

There are numerous antique receipts for brass and metal "varnish." They are all fundamentally shellac dissolved in alcohol, with various colorings or supplemental resins added. Except where the most historically authentic finish is required, any additional coloring of shellac can best be done with alcohol soluble stains and dyes used by cabinetmakers. Mentioned in an earlier posting, "dragon's blood," and "annatto," sometimes spelled "annotto" in old books, but not in the dictionary, were common colorings.

For most clear metal coating, lacquer is the most convenient and practical form of protection. The effect of shellac is pleasing, and is suitable as a way to produce an authentic appearance to pieces which will be protectively displayed, and not subject to frequent handling.

John C. Losch (April 19, 1996)

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Golden Lacquer Finish

Most golden finishes which are not in fact either French Ormolu (applied gold amalgam), or actual gold plate, are color in lacquer. By the time your clock was made, all the American factories were using nitrocellulose lacquer. Color in the lacquer was from transparent dye. The gold tone on many brass musical instruments is produced the same way.

I have a small bottle labeled "Ferree's Lacquer Dye --- Dark Gold---." Source: Ferree's Band Instrument Tools & Supplies. There is no address. I got this bottle about twenty years ago from a musical instrument repairer who got it from his supplier. From that information it should be possible to trace a source through the yellow pages or a business directory.

pleasing gold hue when the mixture is sprayed on bright brass. The right mixture looks like weak orange aid. 1 have even been able to make aluminum and silver look like brass with a similar combination of dye and lacquer.

In October, 1995 1 wrote a rather lengthy instruction for applying lacquer to silvered dials. Most of that text pertains equally to applying lacquer to polished brass, surfaces. If anyone wishes to see that text again, I will E-mail it to individuals requesting copies.

For what the information is worth, many 18th and early 19th C. pieces were coated with shellac to prevent tarnish or to protect the metal. Many recipes of the period advise coloring the shellac with either "dragon's blood," resin from the palm tree, or "annatto.11 I'm not even going to guess what the latter substance was or is. Alcohol stains used by cabinet makers will tone or color shellac, which, untinted, has a natural golden hue on brass. With this knowledge, it is sometimes possible to touch up or "doctor" an old finish when there is reason to preserve it.

On a few occasions I have restored contemporary pieces of apparatus for display using shellac for coating even though it is not as durable as lacquer. The effect is as pleasing as authentic. For those who have access to the book, the Cometarium photo on Page 61 of "The Apparatus of Science at Harvard 1765-1800", by David Wheatland, is a good example of a shellac finish on brass.

John C. Losch (April 13, 1996)

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Spotting Chronometer and Clock Plates

From time to time there is speculation about methods used to employ finishing chronometer plates. That finish is generally referred to as spotting. The term "signature" has been used in this context, and it is appropriate, although I am unacquainted with any "spotologists" able to identify workmen by their spotting.

There are a number of reasons for the markings on chronometer and other clock and instrument plates. For the most part they are attractive and decorative. There is no rule that fine work should not have pleasing finishes to its parts. Magnification will reveal slight imperfections to the polished surfaces where these decorations were applied, and it may be inferred that some decoration served effectively to distract from minor imperfections.

With little exception decoration on brass plates seems to be confined to flat surfaces. This has given rise to the speculation that these surfaces were scraped to flatness in the same manner as cast iron is scraped for fit and oil retention on machinery. Most machinery surfaces, even if scraped or "frosted" in a decorative and even pattern, were so done because these were working surfaces and fit was an essential ingredient of accuracy. There are few flat, scraped, brass-to-brass working surfaces on brass instruments, and I cannot think of any in clocks off hand.

I think it is safe to say, for purposes of this discussion, that the surface decoration on clocks is created with some form of abrasive and some form of relatively soft tool as the device for "scratching" clock or chronometer plates. "Spotting" is the most common name for this kind of decoration. "Watering" is a term I have heard and read to describe the process. "Damas- cening," and "frosting" are both terms better confined to decoration on steel and iron.

In the broadest terms there are two methods of spotting. The first and most widely seen is done free hand. The second method, generally used in shops where there was a large production of chronometers, for example, was done with a device similar to a miniature milling machine with some form of "rubber" which could be raised and lowered against a plate by the operator. The plate in the machine was moved a controlled amount by either a screw or a lever. (Britten's "Handbook" has an over simplified description of a spotting machine under the heading "Spotting.")

I have a third type of spotting tool. This one was used in the Waltham Watch Factory to decorate watch plates. Here, the rubber operates from a vertical spindle, but the spindle can be tilted a little if desired. This allows some shading to the pattern being inscribed on the surface of the plate. There is a table on the machine where the plate would be fastened, which is in a matrix, but it can be moved in any flat direction at the will of the operator. It was by this means that many of the impressive and often symmetrical straight as well as circular designs were put on watch plates. The design was "drawn" by the operator although his "pen" was stationary and he moved the plate under it.

Tools for free hand spotting should be assembled first. The design intended by the decorator will be decided, and a stylus type of tool selected which will allow the chosen design. It can be a piece of wood, plastic today, ivory at an earlier time, bone, rubber such as a pencil eraser, sometimes a moderately stiff steel or brass brush looking like a small paint brush, or just about anything softer than brass that will hold its shape, or return to it upon lessening of pressure. I have had good success with various shapes of ink erasers for some jobs.

After tools are chosen, an abrasive must be selected. It is best to rely on relatively soft, degradable abrasives rather than materials such as carborundum, because by the time this job is in operation, most plates are otherwise completed and pivot holes are in place. Abrasives that will wash away without risk of lodging in a working area are preferable, and all that is necessary.

Pumice is good for coarse designs such as found on hall clock plates. Feldspar found in Bon Ami cake soap is good for many applications. Silver polishing paste, chalk, and even rouge all give various attractive markings. It is better to wet these abrasives into a paste with water rather than oil. They can then be cleaned off with less severe treatment. This reduces the risk of scratching a newly spotted surface.

To begin spotting a chronometer plate, the plate must first be polished to a reasonable degree. Next clean it. There are more ways of applying designs free hand than I would want to try to describe. They are all ways of "writing" on the polished plate. Guides can be used to produce scrolled designs in straight lines. Random patterns stabbed into the brass with a chisel-shaped "popsicle" stick dipped in abrasive are interesting. A rotating piece of wood in a hand tool or dentist's drill offers many possibilities. The combinations are almost limitless.

When guides are used, care must be taken to assure they will not scratch the plate being treated. Anything able to elevate a straight edge just slightly above the plate will solve that problem. As with a dial painter, there is advantage to having a "bridge" of some sort which can be placed over the work, and moved as necessary, so the hand can rest against something other than the plate. Concentrate on the idea that nothing should touch the plate being spotted but the tool or tools being used.

Machine spotting is, of course, very uniform in appearance. On chronometers the device used was proportional to the chronometer in size. Despite this, it is possible to use a vertical milling machine as a spotter. For a rare, one-off job, little preparation is needed. If much of this work is anticipated, it would be worth while to devise some controlled method of advancing the work uniformly. One of the table handles could be replaced with a lever connected to a ratchet so that as it is rocked, the table screw is moved in one direction only. Some form of adjustable stop will assure that the advance is the same with each motion.

In addition, there would be much advantage to fixing a holder for the "rubber" which allows the spindle to be brought down and then released quickly as desired. An attachment held in the milling spindle equipped with a spring for return, and something like a telegraph key to push the rubber against the work would be very helpful. It should be both sensitive enough, and have a wide enough vertical travel, that the operator can control the pressure against the plate by feel. This allows variations of intensity of marks, and it permits spotting a set of plates so that the pallet cock, the mainspring bridge, and the main plate, together while being spotted, all have matching designs.

As with free hand spotting, the tools and abrasives can be varied. Common sense, possibly coupled with a little adventuresome spirit can lead to some very clever expressions. This is the place for the artist inside a craftsman to be let loose.

With the addition of a rotary table I have been able to apply some nicely decorative designs to pendulum bobs as appropriate. Where stars, or in and out designs are contem- plated, it is best to decide a strategy of how far to crank what, then how far to reverse the crank. Write down the game plan, and check off the completed stages, so there is no confusion.

The range of expression is further increased if the head of the milling machine can be tilted a few thousandths. Barring that, shim the work slightly for straight line spotting with shading.

For some kinds of display there is another design which can be very attractive. It is not at all historical in nature. A moire-like effect can be applied to a brass plate by replacing the sandpaper sheet in an orbital sander with a piece of rubber. A section of innertube will serve the purpose. Using abrasive such as feldspar, a polished plate will be mildly abraded in a relatively large, irregular pattern which tends to shift as the plate is viewed from different perspectives. The design varies with whether the abrasive is dry or wet.

Needless to say, any design should probably be done first on a test piece to assure it is what is wanted. Although it is easy to damage a spotted surface, it is rather tedious work to remove spotting.

There are designs found on some factory made clock plates which are not produced by spotting, or any abrasive technique. These designed were generally stamped or rolled into the surface at some stage of manufacture. The dies were rather good, and it is easy to be fooled into thinking these patterns were either spotted, or are the marks of an end-mill. There are other designs which have been produced by chemical etching, or by sand or bead blasting masked with stencils of rubber. I am sure there are other methods not familiar to me.

While it is true that spotting designs are as individual as the shops where they were created, if not as personal as the workmen applying them, most of them can be reproduced or suitably imitated. Many free hand decorations can be repaired. Experiment and study will uncover the secrets of each design's origins.

In today's economy, the controlling factor in treating finishes of this sort is cost. In my opinion, it would be unfair to render a chronometer beyond repair for its owner, when the time to restore or replace a spotted finish will often be economically prohibitive. There are pieces which can be repaired without authentic restoration of spotting, to be enjoyed as lesser lights, even by restorers who do not, and should not be asked to work on commercial grade articles.

John C. Losch (February 16, 1997)

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Bench and Shop Layout

Ordinarily, it is not sufficient for a general clock repairer to plan for only one bench. Any shop planning to perform a wide range of clock services will need a bench for repairs involving a small lathe, use of hand tools, and assembly and adjustment. In addition, a place for cleaning, polishing, and lacquering will be required which will involve at least a sink, a place to polish and dry parts, and suitable ventilation to carry off fumes from occasional use of chemicals as well as vapors from application of lacquer or other coatings. Further, workshops for making replacement parts, or completing complicated repairs, will need a bench suitable for a large vise and a small anvil, not to mention benches for any large machines used for parts fabrication.

Why so many benches or work areas? Repair work to clocks requires an area for clean, delicate work such as pivot polishing, bushing, assembly of movements after repairs, and testing of adjusted movements. Normally, cleaning and hand polishing of parts can be a much messier job than will be the experience from cleaning watches, so an area suited to isolating those procedures from more sensitive work is necessary. Also, a shop where parts will be made or significantly repaired will combine hammering and forging, filing, heating for hardening and tempering, chiseling and scraping, "stoning" or other stages of work anticipating fitting and polishing. Some of these operations involve vigorous physical effort best performed at a lower level than the more delicate operations also included in clock repair.

The main bench is where clock movements may be removed from the case to be examined, will be inspected to determine the extent of repairs required before and during disassembly, and where light repairs, assembly, and adjustment will take place. It should be a comfortable height for both standing and "seated" procedures. Watchmakers' benches are built to a height of 38 inches, and that seems to be a comfortable height for most clock operations. At 38 inches a workman can stand comfortably, and he can sit on a stool with a foot rest for most work where a sitting position is preferred. A repairer can sit at an ordinary office-type chair such as used by typists for assembly which requires a position low enough to see "into" the work.

Space is equally as important for a clockmakers' bench as height. The range of tools, as well as the size of parts, containers for them, and sufficient space to lay these things down in an orderly and convenient pattern demands a large, unobstructed work area. Most people seated at a bench can conveniently reach 30 to 32 inches without straining.¹ If a small lathe is included as part of the fixtures of the main clock bench, it should be to the side of the main work area, but still conveniently accessible. That is, it should not be necessary for a workman to contort himself to be in front of his lathe.

Even if space is at a premium, a bench no less than six feet long is recommended. It could be said that ideal bench will be as long as space permits, since no one has ever complained of having too much bench space.

The perfect dream-bench includes more. Clockmakers need tools; they need lots of tools. Since they need to be able to find them when they need them, they need places to store them until they need them. The bench top is not that place. Drawers are the answer. Probably the shop with too many shallow drawers to contain well sorted tools does not exist. Some thought to the matter of which tools are used most is required, so that the location and size of drawers result in frequently used tools in easier reach than tools involved in less common procedures.

Drawers containing the most regularly used tools and supplies should be placed where a workman can reach into them without having to move, especially from a seated position. This means drawers should be placed in stacks, like a desk, to the side of the workman's knee-hole, or those drawers directly under the bench top and above the lap should be narrow enough to allow opening them with no more inconvenience than moving to the left or right a little. All of this is especially true when the bench is deep, and the drawers are long.

Most drawers for tools and supplies should be two or three inches deep, and can be thought of as trays for tools. Only at the lower level of a vertical bank of drawers is there need for deep drawers. These will contain large, infrequently used devices such as a depthing tool, lathe attachments, a mainspring winder which need not clutter the bench between uses, supplies such as a can of alcohol for a soldering lamp, spare towels, or lunch for a brown-bagging commuter-clockmaker.

The pedestal of the bench, particularly at the front, where the bench touches the floor, should have a generous "kick space." It is very distracting for a workman standing in front of a bank of drawers, for example, to be unable to put his feet under that part of the bench so he can stand close. The best recess dimensions are five inches high and five inches deep. Also, consider putting some shelves at one end of the bench, somewhat in the form of a bookcase.

There are further considerations for a bench where a clock repairer spends most of his working hours. Light is often overlooked until a workman finds himself either trying to operate in shadows or is being toasted by too close proximity to an incandescent bulb. A good quality florescent lamp, with a flexible mount allowing the continual placement of the light for special situations, belongs on every bench. Sources of natural light have both practical and psychological effects. Moreover, there is tremendous value to being in an environment where there is a supply of un-glaring natural light with a pleasant or interesting view. That surrounding prevents the feeling of working in an isolated closet.

Additional thoughts about a clockmaker's bench include having a vise suitable for sawing, filing, and to hold the mainspring winder when it is used. The vise needs to be secure to the bench, and this means it should be screwed to the bench top, in most cases. There ought to be a place to anchor a removable wood bench pin for certain kinds of filing, sawing, and polishing. It is the kind of thing which, if left always in place, becomes an annoyance since things "sticking out" are threatening booby-traps when not in immediate use. The alternative to this is having a piece of wood suitable as a bench pin which can be mounted in the vise as needed.

Ultimately, every craftsman's bench becomes a reflection of what most facilitates continuation of his established work habits. A bench should be a personal statement of what combination of features allows doing the best work its user is capable of doing.

The second bench referred to in the beginning of this text will be about 29 inches in height. For some people, lower is even better. This bench will be equipped with a heavy vise for "serious" filing; it will be the place for hammering, for some kinds of strenuous scraping or polishing of surfaces, and it may be the place for use of heating torches for silver soldering, braising, and heat treating of metals as well. The operations here are incompatible with the work being done on the main bench.

Most people in workshops find the customary height of sinks installed for domestic use is too low for workshop purposes. The sink area should be in the 35-inch range or even higher. Remember the bottom of the sink is below the bench height, and you will be scrubbing and polishing there.

Machine benches should be planned with the machine high enough for convenient observation of positions of tools and work as the machine is being set up.² Many modern tools, and nearly all machines, use electricity. Anyone allowed the luxury to plan a workshop completely should provide sufficient electrical outlets, and they are most convenient when located nearby and high enough to avoid bending or moving things to gain access to them. Try to put them at about chest height on the wall.

Finally, plan cabinets for storage of materials and supplies that do not conflict with the location of tools and work areas. Remember, when planning a clock shop, a place for testing completed work, and a place away from the workshop area for keeping clocks that have been repaired and tested, as well as a place to store work waiting to be done are all highly desirable.

This text was prompted by the question, "What is the best height for a clockmaker's bench?" The answer is a very subjective matter, but it needs to be decided on the basis of at least most of the effecting considerations outlined above.

1) People shrink with age, and 35 inch benches this author built nearly twenty five years ago now require me to stretch to reach things at the back.

2) The experience of this writer is that most machines are placed too low, and I am not tall.

John C. Losch (April, 1998)

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Adjusting Cone Bearing Lathes

There are several things to know about a WW watch lathe, or any size cone bearing lathe, for that matter. Once you understand what the lathe is all about there will be no problem maintaining and adjusting it. Lathes of this type are called cone bearing lathes because the spindle and bearings are tapered. The spindle shapes are actually sections or "frustums" of cones, with bearings to match.

In nearly all such lathes, both ends of the spindle have a thrust angle of 45 degrees, and a lateral bearing angle of 3 degrees. When the lathe was made both the bearing and the spindle were ground to these angles after hardening, or turned in the case of bronze bearings, then lapped to a perfect fit.

If you will look at the front, or collet end of the lathe headstock of most American watch lathes, you will see stamped in the face of the casting either the word "hard" or "soft." This indicates whether the bearings inserted in the cast iron headstock are hardened and ground steel or machined bronze. There is a reason for making the lathes with both kinds of bearings beyond economics, although bronze bearing lathes were cheaper to produce and sell.

According to my friend Leon Levasseur, who worked at the Rivett Lathe Co., manufacturer of watchmaker's lathes, bronze bearings can last as long as hardened bearings. Bronze bearings will seat in faster, and they are more tolerant of grit than the combination of both hard spindle and hard bearing because an occasional particle of foreign matter will bed-in to a bronze bearing rather than continually rotating and scoring either hardened surface at random. In his opinion, bronze bearings are better, but he agrees that there are arguments on both sides, largely controlled by the kind of service required of the lathe.

As a side note, "Frenchy" Levasseur revolutionized the method of fitting bronze bearings and spindles when he decided lapping bearing and spindle took longer than necessary. One day, to the astonishment of workmen at the surrounding benches, he picked up a mallet and slammed the lathe spindle into the bronze bearing. Since the bearing was soft, it took the form of the spindle. The job was completed with lapping, but at the cost of considerably less time than the usual method. With soft bear- ings, the lapping compound was degradable so that if any bedded into the bronze, its effect on the steel spindle was short lived.

Both the life and dependability of cone bearing lathes hangs on adjustment. If one of these lathes were always used with thrust pressure such as occurs from drilling, or working with the job between tight centers, the lathe would always be in adjust- ment and would virtually never wear out. lateral turning, such as staff turning, polishing pivots, or any operation largely concerned with cylindrical surfaces causes the 45 degree thrust bearing to force the spindle out of the bearing. This means the spindle is actually contacting only a small part of the bearing, usually the spot diametrically opposite the pressure from turn- ing. Obviously, enough of this causes an egg-shaped bearing.

Accuracy and reliability of a cone bearing lathe is not a given under all conditions. Cylindrical bearings when VERY well made, and ball bearing spindle lathes with the best bearings now easily available, are more versatile, but not necessarily more accurate than a well maintained cone bearing lathe. This is why all kinds are still made. When a cone bearing lathe is adjusted for the type service required of it, it is the equal of any kind of lathe.

For frequent normal use on the bench of a watchmaker, the bearings should be adjusted as tight as possible so that the lathe will not seize up in use. Prolonged drilling, extensive work turning between centers, or high speed turning for any length of time requires that the spindle be adjusted very slightly looser so that radial expansion of the spindle from heat does not cause the bearings to seize. Common sense suggests that heating would lengthen the spindle, and that the cast iron head would lengthen as well from heat. Actually, the heating is so localized that there is little likelihood of the entire assembly warming enough to change length dimensions, thus the contradictory rules.

To adjust the lathe. Dismantle and clean it first. Liberally coat both the bearings and the spindle with #10 or lighter oil. A good grade of sewing machine oil is suitable. Re-assemble the spindle, being sure to locate the flat spot on the spindle intended to receive the set-screw which holds the belt pulley. Failure to align this pulley makes it possible for the pulley to slip, and efforts to tighten the set screw excessively will lead to damage to the threads in the pulley.

At the rear of the spindle the lathe will have either a single split "nut" which tightens against the rear cone of the spindle assembly, or there will be a nut followed with a lock nut. Most of these nuts are round, have either a slot resultant from being "split", or there will be holes to fit a spanner wrench. In fact, either of these type nuts can be tightened by inserting a small screw driver in the split, or a piece of rod in the spanner hole. Gradually tighten the nut against the cone until there seems to be a little "drag" or resistance as the spindle is turned by hand. Wait a minute or two so that excess oil can be expressed out of the bearing, then see if the bearing still seems tight. If so, back the nut off just a hair, tap the rear of the spindle gently with a light mallet or block of wood, then re-tighten the nut half a hair.

Check the ease of turning again, and repeat the adjusting process if necessary. On lathes equipped with a lock nut in addition to the adjusting nut, tighten the lock nut against the adjusting nut, but be sure to hold only the two nuts with either screw drivers, rods, or spanners, as appropriate. The reason for this is to assure the lock nut is turned against the adjustment nut without changing the setting of the adjustment nut.

Here, I have inserted two paragraphs written by Leon Levasseur after he read what I had written above:

"Regarding split nuts: keep the nut as tight as possible during adjustment to minimize thread clearance, as the final tightening will generally consume the play in the thread as it seats the thread. In general, the thrust is on the thread face away from the spindle and final tightening will drive the nut forward reducing the clearance of spindle thrust by the amount of forward thread clearance.

Regarding double nuts. The same as above, but more severe and with a new twist. For example, the initial clearance attained by adjusting the primary nut causes this nut to bear on the thread angle face away from the spindle thrust clearance. Considerable clearance is now available on the opposite thread face. Now, in the process of using the secondary check nut, lo and behold the clearance goes to pot. Why? When two nuts are tightened on a common thread, each nut is driven to each outside thread face, and the thread backlash inherent in both nuts is equally divided between them at the centerline face of the two nuts. This explains,at least in my experience, why final adjustment with two nuts is not as simple as it appears. One must always under adjust the first nut to compensate for the above conditions."

At this point, whenever possible, it is reasonable to check end-play of the spindle with a dial indicator. If there is no end play and the spindle is free, the lathe is properly adjusted for most repair procedures especially. There should be no run out of the throat of the spindle, where the collet is inserted. If there is, the lathe needs special repairs, another subject.

The final test, optional, is to let the lathe run at moderate speed for five minutes or so. Unless there is perceptible heating of the bearing areas of the headstock, the lathe is fine for ordinary use. If it heats, the spindle is too tight. If the lathe is to be used for extensive single use, as in manufacturing, or if it is to be used for long periods at high speed, a looser setting is best. Under these conditions, it may be necessary to back the adjustment off slightly so that the bearings will be free when they warm up. This requires vigilant checking to get the right combination of tightness relative to use.

Now, another suggestion from Leon Levasseur: "Since the watchmakers lathe was not intended to remove 3 cubic inches of metal per minute I would suggest the following: Two birds with one stone. One "O" ring for two problems. Install an "O" ring between the thrust nut and the thrust face. Depending on the design it may require a hardened or bronze thrust washer for the "O" ring to bear upon. A groove machined into the nut face to receive and capture the "O" ring, leaving it proud .010 t0 .015 is prefered. Nut adjustment mentioned above is now less significant and the bonus is twofold - namely allowance is now available for heat expansion, and a constant load is realized by the bearing assembly. (This means) minimizing dry running and or falling off the tapers. There is zero backlash regardless of machining operation. Thirdly, should the spindle or headstock in general run hot, something is surely wrong with the unit to begin with. If the bearings are set up properly, the load created and decided upon by the "O" ring should last a lifetime if properly oiled. I cannot think of a time that I have ever been fully satisfied with the running condition of a spindle: either too loose or too tight. The above cured it all.

"Have you ever made an adjustment to your liking and found one radial tight spot? Is it the spindle thrust face not concentric radially? Or is the rear thrust face cockeyed? The "O" ring is the cure - it will, in all likelyhood, correct minor spindle error with running time - and lives with and compensates for any thrust face error in the rear."

Check the ease of turning again, and repeat the adjusting process if necessary. On lathes equipped with a lock nut in addition to the adjusting nut, tighten the lock nut against the adjusting nut, but be sure to hold only the two nuts with either screw drivers, rods, or spanners, as appropriate. The reason for this is to assure the lock nut is turned against the adjustment nut without changing the setting of the adjustment nut.

Don't forget about the lathe after it is adjusted. Keep it clean, and dismantle, clean and re-assemble the headstock as often the lathe has been used for dry grinding. This rule is a pain in the neck, but the time required to honor it is less than the time required to earn the price of a replacement headstock. The seals of these lathes are not really more than light dust shields. Oil the lathe frequently. Try to get the bearing to take oil as it is revolving so that you seem to be over oiling. You are really flushing the bearings, and you will have to wipe up the excess oil after oiling.

Finally, the rule of rules. Always loosen the belt on a lathe as soon as you have finished with it for the moment. If a belt is left tight on a lathe it pulls the spindle towards the countershaft or motor, and this squeezes the oil out of the bearing at that spot. When you start the lathe later, it takes several revolutions of the spindle to bring oil to that spot, so that for a few turns there is a portion of the bearing and the spindle running against each other without oil. Like the Chinese water torture, these events have a cumulative bad effect.

In the repair shop, a watchmaker's lathe should outlast at least one watchmaker. I use an American Watch Tool lathe, later Derbyshire, which I bought in 1949 from the son of a watchmaker who had used it all his productive life. The lathe is still good as new, but that is because I have given it the care it deserves.

John C. Losch (5/12/96)

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Replating a Watchmaker's Lathe

This is a hard question to answer because so many of us treat our tools and machines as icons. Appearance is an important factor especially for those of us who want our shops to look like immaculate, sturdy kitchens. I am one of those. (Psychologists have a ball with us. We are compulsive hand washers, adjust all the window shades to the same height, and paint outlines of tools in the garden shed. I am getting over it.)

If you can resist the impulse, I would advise against re-plating the a watchmaker's lathe bed. There are two problems with re-plating. First, it is necessary to remove the old chrome. This involves a reverse plating process which will treat the steel or iron lathe bed roughly. The areas already bare are liable to get pitted before the chrome is all gone from the remainder of the bed. In most metal finishing shops the next step would be to buff the bed to a uniform finish before plating. Buffing is actually a form of grinding, and will have a severe effect on the precision of the lathe bed.

Second, even if the bed were to survive stripping, re-plating requires a special skill on this kind of job. Years ago I used to frequent the plating shop which did Derbyshire lathes. Plating of watchmaker's lathes required constant monitoring and adjusted control of the application of nickel and chrome so that the coating was completely uniform, especially on the "ways" of the lathe bed.

In manufacture of the lathe, considerable attention was paid to getting the ways parallel and of uniform width and height for the length of the bed. Plating had to preserve these dimensions. This means that even the post plating buffing was entrusted to only the most experienced polishers.

Any "after market" plating risks leaving the lathe pretty, but less accurate than it is with worn or damaged plating. If the deterioration on the lathe is patchy, convince yourself that enough of the original plate remains between the bed and attachments so that the lathe is close to original in accuracy. In most circumstances, the only attachment adversely effected on a Lorch-type lathe is alignment of the tailstock. Thus the utility of the lathe in its present condition is really influenced by the kind of work required from the lathe.

If the lathe is so deteriorated that it does need refinishing, it may be wise to consider replacing it with one in better condition. The cost of a beneficial plating job could be prohibitive.

Should you determine to replate, it would be best to interrupt the plating sequence by taking the lathe to a shop qualified to re-scrape the bed after it is stripped. A skillful scraper will restore the alignment of the bed dimensions, although the bed may be smaller. This means the plater will have to apply a thicker plate to assure the bed is the right dimensions to fit the critical attachments, and he will have to have experience with dimensional rather than decorative plating.

If the whole lathe is re-plated, there are problems associated with the necessity to remove the bearing inserts, and putting them back as they were. The spindle bore in the tailstock will have to be re-lapped, and this must be done with concern for parallel and height alignment. Etc., etc., etc.

Plating of lathes is almost entirely limited to lathes intended for watchmakers, because the incidental use of them invites rust. Industrial lathes are never plated mainly because their constant use in an oily environment makes plating unnecessary.

In my opinion the lathe can only be improved in appearance by re-plating, most likely to the detriment of its accuracy.

John C. Losch (May 14, 1996)

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Choosing a Bushing Tool

February 14, 1999
 

 I have strong and rather opinionated views on which is the best bushing tool.  I think it is the K&D.  I will wait for the screams and groans to subside before I continue.  All right, let me begin with the positive reasons.

First, it uses KWM bushings.  I far prefer those to the Bergeon bushings because the diameter, or “footprint,” of KWM bushings is smaller than that of Bergeon.  I have used both, and I find no difference in the quality of either.  That is, both use good yellow brass, and they are well centered with a good finish to the bore.  It’s just one of those cases where size does matter.

Second, all of the clamping system on the K&D is removable to whatever extent may be necessary.  This is also true of the KWM machine.  In most bushing operations, adjusting and using the clamps is unnecessary.  For most clock plates it is sufficient to remove the top half of the clamp assembly, and to adjust the lower part so that it simply keeps the plate at a right angle to the reamer.  If the operator of the tool has properly “relieved” the wear in the bearing being bushed, there is no need to attempt to hold the plate in a position presumed relative to center of the original bearing hole.

 We have discussed this before, at some length on this list.  Relieving a hole is the process of opening the worn hole with a rat-tail file, or other means, so that the once egg-shaped hole is now oval.  When this is done, the reamer for the bushing will center itself between the extremes of the hole so that the reamed hole is centered where the original bearing had been located.

Third, The K&D leaves one hand free while operating the reamer.  This is also true with the Bergeon, but the clamps are not removable.  This is important if the plates are not going to be clamped.  There are two reasons why the plates are best not clamped to the bushing machine.  First, even if the hole has been relieved, unless the egg-shaped hole is perfectly centered under the reamer, the reamer will pull to one side a little, or even break, if it is a small one.  Equally important, many who would invest in a bushing machine are trying to make a living using it.  Time is money, and aligning and clamping plates is time wasted, during most bushing jobs.

It goes without saying, but I will anyway, that the reason the reaming operation should leave one hand free is so that the operator can steady the plate with the hand not turning the reamer hand-wheel.   It is my practice to clean a clock first.  Unless there are unusual repairs to be made to the plates, I polish and lacquer the plates before bushing.  To prevent the plates from getting scratched while bushing worn bearings, I place a paper towel between the plate and the partially disassembled clamps and the anvil.  Bushing this way is fast, accurate, and does not mark the plate.

Fourth, the K&D, because of its simplicity of design, can also be used as a clock staking tool at the same time it serves its intended purpose.  I do not know the exact diameter of the shaft on the K&D, but I am going to guess it is either a standard English or metric diameter.  It looks like it is about half inch in diameter. (3/11/02  I have since learned the shaft is 3/8” in diameter.)  Where the owner is sufficiently creative, staking, riveting, driving, and forging punches can all be made to fit the K&D frame.  One punch drilled to fit the punches in a conventional watchmaker’s staking tool will further extend the utility of the device for clock staking.  Correspondingly, stumps can be machined to expand the versatility of punches made to fit the device.  Needs and problems trigger ideas to expand the utility of this device.

My objection to the other two machines stems from the following.  The KWM is one of those things where someone improved on a good idea.  The original KWM machine, I have been told, was about the same as the K&D.  Later it was re-designed to use the bevel gear, crank, and lever which make using the clamps necessary.   A lever is unnecessary if the reamers are kept sharp.

The Bergeon just keeps getting worse.  Begin with that tiny, easily lost set screw required to install any tool in the hand wheel shaft.  The other two use a bayonet system, which allows quick exchange of tools.  (Bergeon should at least supply a dozen of those screws with each machine.) There should be a separate punch to replace the reamer shaft if one is going to set bushings with a hammer.  I am sure Bergeon does not replace busted handwheels if the operator misses the end of the mushrooming reamer shaft. In the latest refinement comes the ultimate disregard for practicality. The new Bergeon comes with a big plate and three clamping assemblies all held together with MAGNETS!  Just the thing to have on a horologist’s bench.

There is another comparison to be made among the three bushing tools.  K&D is the least expensive.  I have heard no complaints about the product as it is represented.  Both the KWM and the Bergeon are very well made and are proven lifetime investments.

There are alternatives to a bushing tool.  For the hobbyist who has a drill press, the drill-press bushing tool is quite serviceable.   With a good drill press or vertical milling machine, nothing more than a set of reamers and punches are needed to do bushing with commercial bushings.  Other adjuncts can be made with those tools and a lathe.  I know a few old-timers who still make and fit their own bushings with none of the current devices, and I still use that technique for restorations.

Mainwheel, and even center wheel bushings on large clock movements such as hall clocks or antique “grandfathers,” are an entirely different subject.  The tools needed to do it reliably are different, and procedures for bushing worn barrels are a little more complicated than routine bushing.  It is impractical to expect a bushing tool to be able to make every bearing replacement situation simple and routine.

With the biased remarks above, some explanation is in order.  I am half French (although Bergeon is French-Swiss), and nearly half German (KWM is German), but all American.  I suffer from conflicts which I have resolved, in this case, by advocating for what I believe is an American product.  If it turns out that the K&D is made somewhere in the orient instead of New Hampshire, where Kendrick & Davis originated, that is alright too.  I once turned a Chinese Communist into a capitalist, and he is now a millionaire in Canada.   I have no connection with K&D, at least not yet.

Jcl

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Pivot Polishing Techniques

Introduction

There are two fundamental procedures which, after cleaning, are required as a part of repairing almost every clock movement. They are to polish the pivots, and to install bushings. This article attempts to explain the need as well as several basic techniques for repairing or maintaining pivots. Pivots should be completely repaired before any bearing hole is examined for fit, or a bushing inserted.

Why pivots are polished

If I could do only one thing to a clock movement needing repairs, it would be to polish the pivots - to perfection. Ordinarily, clocks operate with what are called friction bearings. That means that a polished pivot is sliding around in a stationary bearing. There are no rollers or balls to reduce the contact friction between the pivot and the brass bearing hole. A pivot has to slide against a brass surface. The smoother the pivot, the less cohesion of metals there is, so the less resistance to a turning pivot there is. This means more motive power is passed through the gear train of a clock to the escapement.

Does that matter? Of course. If rough pivots prevent the required power in a clock to get to the escapement, the escapement will not perform its function properly. This means that the action of the escapement will not be routine, and the clock cannot keep consistent time. It could even mean the clock won't run. Rough pivots, you see, do not act regularly. Sometimes they slip, and other times they grab into their bearings so that the power to the escapement varies with several effects, which, if I begin to discuss them, would drift too far away from the primary subject of pivot polish or finish. To summarize, I would say that a clock doesn't work reliably if the pivots are rough.

There are lots of ways to polish pivots. The method chosen requires some knowledge of the character of the pivot under consideration. A soft pivot will respond easily to simple application of a burnisher. A harder one will require some accommodation; it may insist upon filing first, or even stoning or grinding before it is ready to be burnished. A really hard pivot will only respond satisfactorily to a succession of abrasive treatments.

I have had the privilege of working on a number of precision clocks made from the eighteenth to the twentieth century, and many of them have had pivots too hard to respond satisfactorily to a burnisher alone. Even pivots of this sort get worn, sometimes with grooves which have to be stoned or ground away before the pivot can be polished. In these instances, it is best to do the repairs using a pivot polisher and appropriate laps attached to a lathe, if for no better reason than for the assurance that the pivot will be made to a perfect cylindrical shape. Ancient as the material is, Chapter 11 of Goodrich's The Watchmaker's Lathe treats this subject in good detail. There are other well written and authoritative references on the subject of machine grinding and polishing as well. (See figures 1 & 2)

Figure 1. A pivot polisher or grinder attached to the slide rest of a toolmaker's lathe. Similar equipment is available to fit a standard 8MM watchmaker's lathe

Figure 2. Detail of a pivot polisher set-up with a carbide lap. The lap can be moved toward or away from the pivot shoulder or face, or left in one position, as it revolves against the pivot.

Selecting a Burnisher

There is no argument which will preclude the use of a burnisher for most pivot polishing. The majority of clock repair work can be done with the burnisher in combination with a pivot file where there is grooving or damage to a pivot. Burnishers are commercially available, and it is also possible to make very satisfactory ones from old files. Commercial burnishers are available as a combination tool suitable for clocks. That is, there is a burnisher on one end and a pivot file on the other.

Commercial burnishers are made in two forms: left and right. If you will look at the end of a left hand burnisher it has a profile similar to this symbol: \left\, a right has the mirror image : /right/ , as either is viewed from the end opposite the handle of the tool.

When a pivot is being polished in a lathe, it is customary to run either the file or the burnisher under the work. Here, a right hand burnisher is appropriate because the acute edge gets into the corner where the pivot and arbor face meet. Accordingly, there will be no radius or fillet at that intersection. When a Jacot lathe, or any similar arrangement is used, the burnisher is applied on top of the work, and a left hand burnisher is required. Most shops should have each kind of burnisher, and matching pivot files. One edge of commercial burnishers is rounded since they are made primarily for watch work, and pivots with a conical section, such as a balance staff, need a radiused edge to fit the cone.

I should point out here, that when a right hand pivot file is used with a lathe, underneath the work, the lathe should be run in reverse, since the teeth of the file only cut on the forward stroke. A properly sharpened burnisher will work with the pivot running in either direction.

It is a fact that a burnisher with perfectly square sectional shape will work. With soft pivots I think it has some advantages in that it is less likely to cut material off the face of the wheel arbor, thus shortening the arbor. The grain of the sides of a square burnisher should run parallel with the length of the burnisher. Years ago I made such a burnisher from a file, and I have maintained it with one side of the burnisher dressed with a coarse stone, and the other side dressed on a finer India stone. The coarse side often makes use of a pivot file unnecessary, particularly on the soft pivots encountered on old American "Yankee Strike" movements, and most modern production movements of all origins. Coarse is followed by smooth using rapid light strokes.

Preparing the burnisher

Burnishers have to be sharpened and kept that way. A dull burnisher will "gall" or tear the surface of a soft pivot. Many texts clearly explain how to sharpen burnishers using emery paper attached to a block of wood. This is a very acceptable technique for sharpening. A method I have used satisfactorily is to secure a coarse/fine India stone in some kind of holder. I lubricate the stone with kerosene. Then, holding the burnisher in both hands, I push it away from me over the length of the stone. I have the lead or acute edge facing away from me so that that edge will not get rounded. I guide the burnisher along the stone with my index fingers touching each side of the stone, and my thumbs are slightly pressed against burnisher, aimed toward the center of the stone. I advance the burnisher about a quarter of an inch from right to left and repeat the process until the burnisher is completely sharpened. One side is done coarse; the other on the smoother side of the stone. (See figure 3.)

Figure 3 Sharpening a right-hand burnisher on either a coarse or medium India stone. Push the burnisher forward only, with the "leading" edge to the front to prevent rounding it.

Using a burnisher

Easiest first. Install a wheel in a lathe collet or chuck in the direction that allows the pivot to be as close as possible to the lathe head. If it sticks much more than half an inch away from the collet, the pivot should not be polished in the manner I am about to describe. The best of many reasons for this prohibition is that the pivot will be able to vibrate. This causes a "harmonic" and the pivot will get all kinds of waves and ridges in its surface. Not a good thing.

Select a right hand burnisher, lubricate it and, with the lathe turning very slowly, begin to rub the pivot with the burnisher from underneath. The accumulation of black particles forming on the surface of the burnisher will tell if you have applied the burnisher to the work flat against the length of the pivot. As with a file, run the burnisher over the pivot for the full length of the burnisher. You paid for the whole thing, so you might as well use it all.

Apply as much pressure with the burnisher as you are comfortable with. Pressure is good with a burnisher, but when a pivot is unsupported, it is possible to break a pivot using unreasonable force. A well sharpened burnisher does two things. It cuts some metal away, and is actually acting as a super-fine file. At the same time, it is compressing the surface of the metal to harden it according to the degree of its ductility. It is even possible to stretch the outer surface of a pivot to the extent a layer of metal will peel off. You can be sure a pivot where that might happen is pretty low-grade steel to begin with.

As the pivot is being restored to shape using the coarse side of the burnisher, long, slow, deliberate strokes work best. Once the pivot looks acceptable, wipe the pivot and finish with the smooth side of the burnisher using more rapid, lighter-pressure strokes. Move the burnisher faster, but do not appreciably speed up the lathe. Give the burnisher time to do its job, in other words.

What a pivot should look like

What constitutes a well polished pivot? While there are exceptions, normally the pivot should be perfectly cylindrical in shape. After wiping and cleaning the pivot with pith wood, it should have a visibly smooth surface. There are three additional tests. Slide your fingernail over the pivot. It should slip along the surface, and there should be no grooves or roughness perceptible to touch. Slide the pivot over the edge of one of your upper front teeth. Any roughness can be immediately felt unless your are using store-bought teeth. Magnification from a strong glass or an inspection microscope will confirm the condition of a polished pivot. I have to say that a microscope usually tells you things you would rather not know. A pivot which is really quite acceptable for the majority of clock work will look like pavement at forty times magnification.

Lubricant

A word about the lubricant. I use kerosene. It is the mother's milk of horology. It can be used as a lubricant for polishing, some turning, for drilling of all kinds, as a penetrating oil for loosening things, as tapping fluid, and works almost as well as citronella to keep mosquitoes away. In my more conscientious days I used to mix a tablespoon of USP grade mineral oil from the drug store with three ounces of kerosene for most of the applications listed above. I don't think it makes a lot of difference.

A small covered jar of kerosene kept on the back of the bench will have the stuff handy when needed. I usually apply it with an acid brush, and I wipe the burnisher and re-lubricate it as soon as there is any build-up, or the burnisher looks dry. The kerosene flushes the burnisher so it does not end up rolling metal particles into the surface of the pivot.

How to hold a long arbor in a lathe

There are several ways to hold a pivot in a lathe when it cannot be held close to the lathe headstock. For a large amount of work, it is appropriate to hold one end of the arbor by a pivot, and to support the opposite end in a brass "female center" filed in half and mounted in the tailstock of the lathe. Make a piece of brass fit the taper of the tailstock spindle, or hold it in a drill chuck. Drill a hole the size of the pivot to be polished, then file the metal away to half the diameter of the brass piece so that there remains a groove to hold the pivot while it is being polished. Be sure to run the lathe slowly using this technique.

On most better grade clock wheel arbors there is a chamfer turned at the ends of each arbor. This chamfer was turned at the same time the pivot was turned, and was, therefore, concentric with the pivot in front of it. That chamfer can be mounted in a corresponding sized hole in a disk-type, or "lantern" runner so that the pivot is running, supported, sticking through the disk. It can be polished that way. These disks can be mounted on an angular frame attached to the lathe bed, or they can be made to fit lathe tailstocks. (See figure 4.)

Figure 4. A lantern runner supporting the right end of a wheel arbor by the chamfer located at the pivot shoulder. The left pivot is held against a female center with a face plate and wire dog driving the wheel as the wire pushes a spoke of the wheel.

There are probably more current sources for the information I have touched upon in the above paragraph, but I can cite one rather obsolete source in addition to Goodrich's book mentioned above. In 1964 I wrote an article on pivot polishing published in the NAWCC BULLETIN, whole number 112, October, 1964. It tells how to make a disk-type holder for wheels. Beware that the illustration shows the wing-nut holding the disk to its frame positioned on the wrong side of the disk.

Another way to polish pivots

Close to fifty years ago I spent some time under the tutelage of Albert Rozsay, a watchmaker in New York City, who learned his trade in Hungary before World War One. He never saw a watchmaker's lathe of the type we are familiar with until he visited Rome after the war. There, he was mesmerized by an "American" lathe with a foot wheel to power it. Much of the work he learned to do was done with a block of wood, a pin vise, and a file or burnisher. I saw him turn a watch staff that way! He taught me to make taper pins, long tapered rods such as are hammered and formed in brass and steel for lever springs, and to polish pivots by that method. It is the method so well described by Dr. Goodman in an internet posting of 4/18/98.

The technique involves holding a pivot or an arbor in a pin vise with the pivot to be repaired on the opposite end. The pivot to be repaired is rested in a groove in a block of wood usually held in a vise. The pin vise is revolved with the fingers of the left hand, ordinarily, so that the pin vise revolves more than 360 degrees pr. cycle. The whole process is reversible for left handed workmen, The left hand burnisher is applied to the pivot so that the burnisher is always pushed or pulled in the opposite direction of the rotation of the pivot, or pin vise holding the pivot. (Right hand burnisher applied above the work for lefties.) Inevitably, the pin vise, in the operator's left hand, usually, will rock up and down slightly. Not to worry. If the burnisher is presented to the pivot firmly enough, it too will rock with the pin vise. In effect, the pivot burnisher will always remain flat against the pivot. (See Figure 5)

Figure 5. This process is only effective when the workman learns to roll the pinvise from the heel to the tip of his thumb so that the pinvise turns more than 360 degrees.

With Dr. Goodman's permission, I quote his description below:

". . . so I will offer a "brief description", as you ask, of how you can start, not having been made aware of what machines, tools or materials you have.

"Yes, the pivot should be supported. A way to do that is to use a block of any hard wood clamped in your vise, thicker than any pivot you may polish, on the top of which you have filed v-grooves of various depths to support various pivots. The block should be high enough to provide clearance to the vise jaws for a nearby wheel on the pivot's arbor. A suitable pin vise clamped on the other end of the arbor, is in your upheld palm, thumb toward the vise. Practice rolling the pin vise between thumb and along towards the end of your forefinger so the pivot lies flat in the groove and rotates continuously in one direction (depending on the location of the pinion and the wheel, you may dispense with the pin vise and rotate the arbor, directly).

"The other hand holds the lubricated burnisher and its full length repeatedly strokes the pivot against its rotation. Considerable firm pressure may be used, consistent with the care needed to avoid bending the pivot! The burnisher is a rigid, smooth strip of hardened steel which has been "made" by sliding it under pressure on flat, medium abrasive cloth or paper so the acting surface has crosswise scratches. If carried out properly, this repeated action should burnish (polish and harden) the pivot and will not removed metal to change the pivot's fit in the pivot hole. It takes some practice which should be done on "practice" pivots. And I advise that you do not attempt French Clock pivots until you have mastered those on American Clocks!"

This really is the most sensible method available once anyone adopting it has learned to make the pin vise (actually, a pin chuck) rotate over 360 degrees. After a few hours of practice, it is possible to polish pivots with more pressure than allowable when a pivot is unsupported. The time required to grip a pivot or arbor with the pin vise is considerably less than the time required to set up a wheel assembly in a lathe. The real secret to success with this method is to have good quality pin vises with small diameter, diamond-pattern knurled handles. Starrett and General, tool manufacturers, both make such vises, to my knowledge. There are probably other producers as well.

Other methods, briefly mentioned

I encourage anyone serious about learning any part of horology to hone your "library" skills. It is all there, you will discover, after you learn to find the information you seek. I sometimes ask myself if there is anything I can add to the wealth of available information in print. Pardon the "commercial," but, for those who do not have reasonable access to suitable libraries, the extraordinary NAWCC Library is available to NAWCC members through the mail, and even E-mail, for some purposes.

The Jacot lathe is well described in numerous reference books, both old and new. There are some large ones available, suitable for clock pivots. It is possible to make a variation of the Jacot lathe, and a conventional watchmaker's lathe is a suitable foundation for making such a device. A larger lathe would allow a variation of the Jacot lathe which I have used for a number of years.

I made a disk of tool steel about 1/8 inch thick, and drilled a series of different diameter holes around a concentric circle scribed on the disk. The scribed circle was an inch in diameter. I then turned the edge of the disk down to the scribed line, so that I was left with a series of half-holes around the edge of the disk. I hardened and tempered the disk. I left it nearly glass hard, tempering it just enough to take out the brittle character of glass-hard steel. (Hardening and tempering are subjects to be left for another time, or to be researched by the reader.) Next, I polished the half-holes using appropriately sized wires, and slightly rocking the disk as it ran against the wires charged with aluminum oxide. This left the grooves, intended as rests for clock pivots in a slightly crowned or "olived" state. It meant that the pivot would be resting on a smooth, slight hump, and would not have to touch the sharp edges at either end of the groove.

I made an assembly, left to the imagination of the reader, for purposes of this discourse, which allowed me to hold the hardened, grooved "pivot rest" in the lathe tailstock; in alignment with the center line of the lathe. I made the holder for the rest adjustable so that I can raise or lower the rest-disk to align it. It must be getting obvious. I insert a rod, or project the back of a drill from a collet or chuck in the headstock of my toolmaker's lathe, selected to fit the opening in the handle of the pin vise. A bow, about a foot long, has a thin nylon fish line wrapped once around the knurled handle of the pin vise. This substitutes for the pulley attached to the work on a Jacot tool. (See figure 6.)

Figure 6. A variation on the Jacot lathe. A pin vise tightened on a wheel arbor or pivot is supported by a rod in the headstock and turned by the bow. The opposite pivot is burnished as it is supported by an appropriate groove in the hardened steel rest.

Grip the end, or, if necessary, the pivot opposite a pivot requiring work, in a suitable pin vise. Fit that pin vise over an appropriate rod (as described above), rest the pivot to be repaired in the disk-rest supported in the tailstock, and file or burnish away. For pivots so hard they have to be stoned, ground with a brass, bell-metal, cast iron, or zinc lap, I use either boxwood or even Plexiglas rests made the same way as the hardened steel one, although I do not bother to "olive" the groove. Needless to say, I hope, a new, clean rest must be used with each change of abrasive. When I have an opportunity, I will write an illustrated article about this device. I have been planning it for about ten years.

In THE WATCH REPAIRER'S MANUAL, Henry Fried described a polishing shovel to be used with suitable abrasives. The text goes from page 160 through 164. (PP 149-160 for people interested in the Jacot lathe.) It involves a roller or pin to be fitted to the tailstock of a lathe, a piece of brass or iron pipe cut in half and filed across the section, charged with polishing compound, and rubbed against the pivot mounted in a lathe or steady rest. One half of the shovel rubs the pivot while the other side is steadied by the pin in the tailstock. Separate polishers or shovels for each grade of abrasive. It works. Once, when Henry visited my shop I showed him my brass shovels. He said, "I told you use iron." I replied that his book said either brass or iron. "So can't I forget something once in a while?" he asked. He forgot more than most of us will ever know.

No craftsman worth his salt uses hole closing punches for anything, would ever clean any clock movement in an ultrasonic without disassembling it (even for his brother-in-law), or would even think of buffing a pivot. I do not claim the virtuous reputation of some who have never strayed from the printed rules of our venerable predecessors. I willingly plead guilty to having buffed pivots on occasion, and, during this session of soul bearing, I have buffed a pallet face or two as well.

How could I do that? Easy. In addition to having an inspection microscope, I have a pathologist's microscope. With the latter it is possible to see particles of abrasive if they are present or embedded in the surface of a pivot. With an ultrasonic cleaning machine, and using it in time, i.e. before a pivot is inserted in a brass plate and spun around to check its fit, the likelihood of contaminating either a bearing or pivot is reduced unless the abrasive is one not degradable, such as diamond powder.

An abrasive which is marginally softer than the material it abrades will work before it fails. That is why softer abrasives will work on harder materials, even if their effectiveness is short lived. This happens because the sharpness of an abrasive particle cuts briefly at the same time the particle dulls in response to the superior hardness of the material it is trying to cut.

So what's the deal? There are occasions where I polish a pivot and find one prominent groove left in it. If I were to reduce the pivot sufficiently to remove that groove, the pivot would be too thin to support the arbor of which it is a part. Particularly if that groove is near the outer end of the pivot, or if the condition exists high in the gear train, it could be impractical to re-pivot the wheel because of that groove. After the pivot has been polished by burnishing, in the conventional way, it is reasonable to refinish the pivot and leave that single groove. BUT, the edges of that groove are sharp, there is deformity or "crush" to the bearing surface when it is under load, so that sharp edged groove will cut the bearing. The pivot, in that condition, is useless.

It is possible to rationalize anything. Ever hear of an oil groove? If, in the condition described above, I could dull the edges of that remaining groove, I could render it harmless. A buffing wheel, with red iron oxide rouge, will do that. If an otherwise well-polished pivot is exposed to a rag or felt wheel, and rotated against it for a short time, the edges of the groove will be abraded and the groove will be rendered relatively harmless. Sneaky, but appropriate when the technique is applied with intelligent judgment.

A more important question is, "How did that groove get there in the first place?" Check the condition of the bearing hole in the clock plate. A piece of significant abrasive material may be lodged in the brass bearing, and a bushing may be in order. Keep cause and effect always in mind.

All of the tedious above is not actually all there is to say on the subject of pivot polishing. I realize that I have almost beaten the issue to death, but there is really much more to be said, or, perhaps, better, repeated. I have said much of what I think, and there is considerably more to be said by me and others more learned than I. There is, however, a "bottom line." It is, get the pivot smooth as a baby's behind.

John C. Losch (May 27, 1999)
 

Book references:

1. Goodrich, Ward l., The Watchmaker's Lathe, Hazlitt & Walker, Chicago, 19??

2. Fried, Henry B., The Watch Repairer's Manual, D. Van Nostrand Company, Inc., Princeton, N.J., 1961

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Why Clock Pallets, Pivots and Bearings Wear

9/23/98

 As the relevant sophistication, and the diverse backgrounds of people interested in technical horology grows, so, too, do the questions and challenges to long established "conventional”  wisdom.  If we are to challenge the conventional wisdom, we are going to have to approach the matter in a scientific way.  Those who have undertaken to experiment with established procedures or knowledge can attest that it is difficult to even agree on what constitutes the scientific method.  It would be presumptuous for me to try to define it.

 During my productive years I didn’t question a lot of the information that came to me.   I was something of an empiricist drawing on the experience of my teachers.  I made changes to procedures and techniques only when the need for change threw itself across the path I was traveling.  I did, however, seek and find the conventional wisdom.  Much of that, I might mention, goes back to sources originating in the eighteenth century.  It has been repeated in print to this day, although scholars of published material may have noted that the techniques of many authors did not include quote marks.

 Wear on pallets and in bearings represents a cycle.  It has been viewed traditionally that the wear on steel at first exceeds the wear on softer brass, but eventually the condition reverses, then reaches equilibrium until the clock, in these considerations, will no longer run.  Abrasive dirt becomes embedded in both escape wheel teeth (at the points), and in the contact point within a clock train bearing.  The embedded dirt abrades or laps the steel until the surface of the steel becomes sufficiently rough to file the softer brass surface.

 As an aside, little mention has been given to how much of the abrasive quality of brass comes from impurities in the brass itself.  There are probably metallurgical studies dealing with this subject, but I have not looked for them.

 Continuing the cycle, a rough pivot files away the abrasive-charged surface it turns against, releasing an increasing amount of abrasive laden particles to circulate in the oil of the bearing.  Some of this is a result of the active end-play of wheel arbors between the plates.  With pallets, the cycle is a little less dramatic unless there is a wobble in the pendulum which causes the pallet arbor to vibrate between the limits of its end play.  Then, the grooves worn into the pallets will file a little on the ends of the escape wheel teeth.

 It becomes apparent that gritty oil gets between the pivot surface where it touches the bearing, and the pivot.  So the cycle repeats, probably at increasingly shorter intervals.  Probably too, the trading of effects reaches a balance where they are nearly simultaneous.

 If this scenario is true, what do we learn from it?  First, I have read texts suggesting that harder bearings would delay the wear cycle.  My own experience is just the opposite.  Soft bearings are able to absorb abrasive more readily.  Thus, the abrasive is pressed deeper into the bearing surface.  This means that the particles of abrasive stick up less in the bearing, and they cannot take as big a "bite" into the steel.  I repaired a Lemuel Curtis movement from a public clock known to be in constant use since 1848.  The plates are soft, the pivots are both small and hard, and in 1996 I installed the first bushing the clock ever had.

 We also learn that the cycle of wear to bearings and pivots seems to occur at increasingly shorter intervals.  Some new clocks will run for twenty years before repair.  After that, however, it seems that they need service more frequently.  All of us have been taught the purported value of pegging out bearing holes.  It should be done, but it is not enough in many instances.

 Some background leading to my point.  Bearings are, as the name implies, something for the wheel pivots to bear against.  If a clock were assembled, wound up, then the plates pulled apart, wheels would be flying in all directions. If there were time to observe the fact, most flying parts would be traveling in a straight line until gravity pulled them down.  This is an application of Newton's first law of motion, paraphrased: A body travels in a straight line unless attracted by an outside force.  Gravity, or the wall, became the outside force in this experiment, but normally, bearings become that "force."  That "force" forces the clock wheels to travel in a circle.

 The desire of clock wheels to travel in a straight line causes wheels in gear trains to try to spread apart, but the bearing defeats this impulse as well.  The direction the forces of resistance and power try to move becomes the point in a clock bearing where the pivot is pushed against the bearing. That point is where the bearing wears.  The mathematical name for analysis of the direction is "Vector."  I am not qualified to explain the process further.

 If a clock has a bearing hole fifty thousandths of an inch in diameter, and there is a pivot of forty five thousandths, there should be one infinitely small point of contact between pivot and bearing.  Not true in the real world.  There is a matter of crush or deformity of the two surfaces involved, so there is greater surface contact than might be imagined.  That contact, with resulting friction as pivot slides along bearing, is controlled by the force of the spring as it is delivered along the gear train.  There are, of course, numerous additional deformities and frictions to rob motive power in a clock as the force works its way to the escapement.  Oil in a bearing helps to reduce the adhesive friction present where pivot and bearing meet.

 "What's your point?" you're asking if you are still here.  It's this.  Pivots contact only one spot in their bearings, they ultimately wear the bearing oval to a greater or less degree, and that is also the spot where abrasive becomes embedded in the bearing.  If the wear of a bearing under consideration is slight, it is unlikely there will be a bushing installed.  That decision should be based considerably on the type gearing, coarseness, and suitability of the depthing in the train.

  SO, the bearing passes the wear test, it gets pegged out, the pegwood slips around the unworn part of the bearing, and the tiny abrasive crescent of wear escapes the revolving pegwood.  Sadly, that leaves the clock with a bearing ready to resume its "dirty" work when the clock is returned to service.  I think this explains why the running time diminishes between repairs on older clocks.   Even if pegwood reached a spot in the bearing charged with abrasive, it is unlikely that pegwood could dislodge abrasive pushed deeply into the bearing surface.

 There are several ways to improve a charged bearing.  Hjalmar Olsen, one of my teachers, recommended putting a fine five-sided reamer through the pivot holes of French clocks in particular.  If the reamer couldn't be made to revolve with light pressure, a bushing was probably needed anyway, because the hole is worn out-of-round. If the reamer scraped a slight amount out of the bearing, including the abrasive-charged area, it is true that the bearing hole would be enlarged by one or even two thousandths of an inch. In most cases it doesn't matter!  All except the charged point in the bearing was doing nothing to help the clock run, and the depthing of the train is effected only by the amount the abrasive part of the bearing was enlarged.  The pivot and its wheel will have a more nearly permanent location in an abrasive-free hole than in one immediately lapping or scoring the pivot smaller.

 There are two precautions required when a bearing hole is reamed.  First, it is necessary to be honest about the looseness of the hole.  The above rationale cannot justify excessively loose bearings.  A combination of experience, understanding of depthing, and good judgement is needed.  Second, if a bearing is excessively loose, the oil in the bearing will not be retained by capillary attraction, and it may run away from the pivot.  Be careful when using this technique to “clean” pivot holes.

 On larger clocks there is another procedure available.  After a hole has been cleaned, pegged, and examined to see if a bushing is not needed, the abrasive surface may be “ground” away using powdered feldspar (Bon-Ami cake soap pounde