Shop Note

Draw Plates – Their usefulness in Ship Modeling

John O. Kopf

Draw Plates occur in two varieties – those use by jewelry makers to form various cross-sectioned cylinders in metal, and those used by ship modelers to small-sectioned cylinders (usually round) in wood; primarily for use as Trunnels.

Jeweler's Drawplates

A variety of Jeweler's Drawplates, illustrating the variety of hole-shapes available. Also shown is a pair of drawplate tongs.

A drawplate consists of a steel bar with a number of holes if graduated size. You can buy jeweler's drawplates with round, square, triangular, hexagonal, octagonal, elliptical, and other-shaped holes. The holes are used to shape metal rods (wires) and tubes to an external cross-section, that will correspond to the shape of the holes in the drawplate. The results are rarely used as-is – they are instead stock used for further jewelry construction. Drawplates tend to be fairly expensive; the price will vary depending upon the number (and shape of) holes and the hardness of the plate. One can find drawplates made in India for $10-$20 (but they are relatively soft, and wear easily), and fine drawplates from France and Germany for up to hundreds of dollars, each!

Although rarely used for metal by ship modelers, they do have their uses. For example, round wire can be drawn into a square cross-section drawplate, such as needed for "Hammock Rails".

Illustrating the use of a drawplate (from Oppi Untracht's Metal Techniques for Craftsmen).
Each hole has a large end and a small end – the small end determines the resulting size! The metal is "greased" with Beeswax, inserted into the large side of the hole, and pulled from the small side (think of pulling taffy through a funnel). If you re doing a lot of this work, you should invest in a pair of drawplate tongs. But, if only doing it occasionally for small quantities, you can get by with a pair of pliers. Note also that the bigger the size reduction in one pass, the harder you will have to pull (the commercial draw tongs have a hook on one handle, so they can be connected to a small windless if necessary). And, for each drawing pass, the stock will work-harden, making subsequent draws more difficult – plan to anneal the stock regularly!

For further details, there are a number of good books available on such metalworking techniques. I have, and can recommend, Oppi Untracht's Metal Techniques for Craftsmen.

Drawplates for Wood

A couple of home-made Drawplates.

For wood, ship modelers use the drawplate "backward". The wood stock is inserted from the small side, and the edge of the hole is used to shave a layer of wood off the cylinder. Because of the expense of jeweler's drawplates, modelers often attempt to find a less expensive substitute. One such substitute is a "Drill Gauge"; a piece of sheet metal with a progression of holes that correspond to – and is used to size – twist drills. However, these tend to be fairly soft, wear rapidly, and then the holes get bigger.

It's better to make your own. I've made several different draw plates

The largest one is in 1/8 x 1 x 36" (cold-rolled - the black stuff, or it may be plated) steel. I drilled a series of holes from 1/2" to 1/16" from one end to the other in 1/64" increments. I use this one to draw down spars to size (I make all my spars from split wood to insure straight grain and no warping); I can also push the spar stock part-way into a hole to produce a rough taper - easy to sand smooth later.

A second started with a 1' length of 1/8 x 1/2 cold-rolled steel. It's like the first, but the holes go from 1/8" to 1/32", in 1/64: steps. The shorter length makes it more convenient at the bench.

A third started with a 4" length of 1/8 x 1/2 Bright steel (this is shiny - not plated). I drilled a series of "dimples" half-way through the metal, using a 1/16" drill. I then drilled a series of holes: #60, #61, .. #80 starting at one end. I use this one for making trunnels.

There will be unused dimples at one end - as the holes wear larger, you can re-drill the holes larger, extending the series into the empty dimples.

Once all of the holes are drilled, turn the plate over and file off any burrs. This will leave sharp edges. Insert the wood from this side to shave off the edges.

I use bamboo for trunnels. Bamboo varies in quality; it also varies radially (the outside is glassy {brittle}, the inside is "punky" (crumbly}). Avoid the "joints" - the grain there is wild!

When splitting the bamboo, split the pieces into successive Halves...if splitting near an edge, the split will tend to wander toward the near edge.
{John O. Kopf}

I'd like to add an additional hint for making small dowels. I don't use a drawplate, but rather a heavy drill gauge -- usually #1 to #60. Again, get your drill gauge at the flea market because modern ones are made of crappy steel. If you want new (and pricey) buy the Starrett#186 for small dowels and/or the Starrett#286 (#61-80) for treenails. Let's say you want to make a dowel that's 0.07" in diameter, corresponding to a #50 drill. Start with a square piece of stock, say 3/32 that will easily fit through a larger hole, say #40. Push the stock through the hole enough for you to grab. Now pull through at a shallow angle, say about 10 degrees. That will shave off one corner. Repeat for each of the other four corners. Now go to the next hole, say #39, and repeat, pulling through and turning 90 degrees for each successive pull to shave off another side. Continue until you're at the size you want. The fit through the hole should always be loose. You are shaving wood, not trying to draw down metal.
{Boris Beizer}

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