I found no reference to Sandpaper in your terrific
FAQ. I am curious as to what grades of paper I will need. Regular
or wet/dry sandpaper? I purchased a set of the fine files, but no sandpaper yet.
Thank you!
{Jeff in San Diego}
Sandpaper (equivalent to the British "glasspaper") consists of an abrasive (in
a specified grit size) bonded to a flat backing (it also comes in belts, bands,
drums, and disks for power tools). There are a large number of backings,
bonding agents (the glue), abrasives, and coatings.
What you will need depends on what you are trying to do. 12000 grit is great
for polishing paint, but not much use for hogging material off a
bread-and-butter hull.
Backing
Backing materials may be a variety of paper, cloth, plastic film, and mesh;
paper is the most common, but shreds easily. Cloth is tougher, but can tear.
Mesh provides a cushion, and allows the dust to escape.
Bonding Agent
"Wet-and-dry" is waterproof; most others aren't. The only reason you're likely
to want to wet it is to polish a finish, or for sharpening tools.
Abrasives
-
Sand (no, not the stuff off the beach – that has been ground smooth, and you
want sharp edges!): the oldest abrasive (and probably least useful any more).
Actually consists of ground-up quartz rock.
-
Garnet: Although inferior to modern day abrasives, has a soft cut and leaves
the smoothest finish of all abrasives; therefore well-suited for final sanding
of wood surfaces.
-
Aluminum Oxide: the work-horse of sanding; long-lasting and often called
"production paper". Real "emery" is a variety of Aluminum Oxide.
-
Silicon Carbide: Very hard black material; usually the abrasive on "Emery
paper"; commonly found as "wet/dry" sandpaper.
Coatings
Some sandpaper may be coated with zinc stearate; this is a waxy material which
helps keep the sanding residue from clogging the paper; useful for sanding paint and
plastics.
Grit
The size of the grit is measured by the size of a screen that the grit will
pass through. 100 grit is (roughly) equivalent to 1/100th of and inch. Not all
abrasives have all grits available.
| Common Size | (Grit) Sizes
|
| course | less than 60 grit.
|
| medium | 60, 80, 100
|
| fine | 150, 180, 220
|
| extra fine | 240, 280, 320, 400, 600
|
| super fine | 800, 1000, 1200
|
| polish | 1500, 1800, 2400, 3200, 3600, 4000, 6000, 8000, 12000
|
Sanding
There are a number of common rules for sanding:
-
Back up the sandpaper with something hard – just holding it in your hand will
likely generate humps and hollows.
-
Sandpaper scratches the surface, and stays sharp by shedding abrasive. So,
clean the surface thoroughly when changing to a finer grit – otherwise a
courser grit may turn up later and make big scratches; then you'll have to go
back to that size grit paper and start over.
-
NEVER sand until all cutting is completed – those same grids that have been
shed can quickly dull your cutting edges!
-
Changing from one grit to another within a common size doesn't buy you much;
going from one common size to another does.
{John O. Kopf}
I use emeryboards for a lot of coarse sanding. They are cheap, can be cut to any
shape of tip you want, or to expose fresh sanding surface, and you just throw them
away when used up. I also use a thin springy piece of wood, about a half inch wide
and 9 or 10 inches long with # 220 wet/dry paper glued to it. When fresh it's 220,
when used a while it becomes about 400. It is quite durable, you see. I also have
a selection of round sticks, paint brush handles, that sort of thing, in different sizes,
which get wrapped with the wet/dry for doing inside curves. I have foam back
sanding blocks which are sort of OK, but they blend too much and are too large
for many places. They work best, used lightly, for the outside of the hull. For a
thickness sander I lay a stick with paper over two blocks the right thickness and
pull the work piece under it. You don't need high-tech.
{J B Sanborn}
I usw sandpaper I buy from an automotive store(probably used for body work). It
comes in rolls about 6" in diameter, yellow in color with adhesive on the back.
It does not load, lasts a long time (a roll should last for years). I have it
in 80, 100, and 220 grit. Cost is around $30-$40 a roll. I stick it to shaped
blocks, aluminum t-bars, popsicle sticks and even wire and dowels. For finer
sanding I use wet dry in the finer grits.
{Kirk Gullach}
Try "Klingspor Gold" non-loading sanding sheets. They are cloth backed sheets
and rolls that really do not load up unless you're sanding a finish that has
not quite dried. The sand "paper" is available in grits from 80 to 400 and are
relatively pricey but definitely worth it. I've been using the material on
ship models and wood carvings and am very satisfied with the performance. They
have a website.
I've no connection with Klingspor except as a satisfied user.
{Roy Ozaki}
Jeff, I think it depends on the finish you want and what you are using for a finish.
There is a place for 400, 600, and fine steel wool but they don't do much for
shaping and sanding planks into a level surface (on this scale, sanding replaces
planing pretty much). On my ship's deck I tried to acheive that bowling-lane
sheen with 600 and 800, etc. but the grain is just too big and the wood too soft
to polish the wood that way. But after about 12 coats of urethane and buffing
with some really fine stuff (don't remember what I wound up using, sorry) it
came out really nice. But a lot of people don't want the polished furniture look.
I do. You have a lot of choices. I keep a box full of a big variety. I chose not to
use the automotive stuff -- it is wonderful but the expense was too great an
investment for me. I use wet/dry, some garnet, I'm not too picky about type.
{Gary(osmbird)}
Wet or dry sandpaper, used wet, is wonderful for sanding material which would
otherwise load up the paper after a very few strokes. As you say, it is best for
cutting the "finish;" e.g., paint and varnish, but also for epoxy and plastic ...
anything that will melt from the heat generated by friction.
From a post the other day which suggested that used 320 grit was equivalent to 400
or something like that, No, what used 320 is is a very ineffective tool. New, sharp,
unloaded paper cuts quickly and has no large particles to leave gouges. Old used
paper is loaded with junk that keeps it from cutting and just has fewer of the
boulders that hog out material.
Now if I could just find a source for wet-or-dry, self-adhesive, 6" disks for my pneumatic
random orbital sander ... but that's not for models.
{Roger Derby}
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