help needed. How to sand a piece of resin perfectly flat

Lonnie Sweet · Post by **Lonnie Sweet** » Wed Jul 30, 2014 12:25 pm

Hi guys, I need help. Im having a hard time getting the mating surfaces of two pieces of resin absolutely flat. Any tips? I usually go super slow sanding lightly and testfitting often. But for some reason this piece just refuses to play nice. Any tips I can try?

Kylwell · Post by **Kylwell** » Wed Jul 30, 2014 12:48 pm

3 words, Big Flat File.

Mine is 14x1 inch. Because they don't bend @ all you can end up with a absolutely flat surface.

WarpeD · Post by **WarpeD** » Wed Jul 30, 2014 1:33 pm

If the surface is large, I'd suggest getting a nice 12" x 12" thick marble or granite floor tile from Home Depot or Lowes, and then taping a piece of appropriate grit sandpaper to the surface. This product is very flat, rigid and robust. Then, applying light pressure only over the center of the surface to be flattened, make gentle passes in one direction only, back and forth. Remember that resin is very soft. Patience is a virtue here, and too much force can work against you. This sort of question comes up in many places besides plastic modeling.

Chas · Post by **Chas** » Wed Jul 30, 2014 4:15 pm

Yep, in tooling set up and marking out they call 'em surface plates. Usually made from granite, glass or sometimes cast iron. For plastic model building a granite floor tile would be a good substitute. I wouldn't put the tape underneath the sand paper though. I'd make it smaller than the surface of the tile and tape the edges down.
A good BIG file is always a good thing to have around as well.

WarpeD · Post by **WarpeD** » Wed Jul 30, 2014 4:21 pm

That's what I was thinking of when I made that suggestion, Chas. I ran into surface plates for the first time last fall in an entry level machine tool class. Mistreat that great big block of rock and teach would be all over us.

Kylwell · Post by **Kylwell** » Wed Jul 30, 2014 4:34 pm

Yes, that works great too. Just check often and change hand positions to avoid putting your pressure more in a single spot. I use a 12x12 piece of marble I got on sale @ Lowes for $1.75.

Rocketeer · Post by **Rocketeer** » Thu Jul 31, 2014 8:37 am

Lonnie Sweet wrote:Hi guys, I need help. Im having a hard time getting the mating surfaces of two pieces of resin absolutely flat. Any tips? I usually go super slow sanding lightly and testfitting often. But for some reason this piece just refuses to play nice. Any tips I can try?

Why make it flat? When I have two big flat surfaces to mate, I often make them both slightly concave. That way I can fine-tune the fit at the edges, and not worry about the center at all. Heck of a lot easier. Glue the pieces together with five-minute epoxy; it'll fit the cavity and you'll get a good joint.

sbaxter · Post by **sbaxter** » Thu Jul 31, 2014 8:42 am

I use a few pieces of flat steel I got from the machine shop here at work -- some are smaller but thicker and relatively heavy, and one or two are thinner (between an eighth- and a quarter-inch) but with much more surface area. Some of these also make good pieces to use for evenly distributing clamping force, depending on the piece being clamped.

Qapla'

SSB

dizzyfugu · Post by **dizzyfugu** » Fri Aug 01, 2014 3:02 am

Kylwell wrote:3 words, Big Flat File.

Mine is 14x1 inch. Because they don't bend @ all you can end up with a absolutely flat surface.

Second that. If it is too large for a file, you can also put a sheet of sand paper under a flat, stable board (not too thin and light, so that it does not bend at all! Marble sounds very good.) and use that, with some water, in a circling motion. A sheet of sand paper wrapped around a cubic piece of cork also works well (frequently used by carpenters, and also on car bodies).

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help needed. How to sand a piece of resin perfectly flat

help needed. How to sand a piece of resin perfectly flat

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