"Gluing" SiC wet or dry to a surface plate with water

My apologies if everyone else knows this already. But this might save someone else from reinventing the wheel.

I have for many years used wet or dry SiC paper on a B grade 9 x 12 plate for lapping. I wet both sides of the paper and press it down on the plate with my fingers. I suspect a lot of people do this. Good paper (e.g. 3M) stays flat. Bad paper curls at the edges.

Today I was evaluating some 7000-15000 grit paper I bought via Amazon which was made in China but has "German Technology" printed on the back.

For some reason I got the idea of using the soft rubber printer's brayer I use for spreading spotting media to stick the paper down. The result blew my mind. The adhesion was so strong that the paper simply would not slide. It would lift off with no effort, but was extremely resistant to shear which is what you need for lapping.

Using water only lets you switch grits, or wash off swarf effortlessly. Peel the paper up, rinse it off, wipe off the plate and stick the paper back down. Done properly the plate will experience almost no wear.

I'd been planning to make a set of Robin's sanding plates in several grits, but after discovering what a change the brayer made I'm sticking with water and stone. The brayer will even control horrible paper for a while. Stuff that curls up into a 2" tube when it dries.

Reg

Where do you buy your SiC paper?

Varies. I try to get 3M papers, but I've had problems getting what I wanted.

I recently got 1500-7000 German "Matador" brand paper from LANHU via Amazon and Chinese made 7000-15000 grit paper marked "German Technology" from the same Amazon seller. The Chinese paper appears to be of similar quality to the German.

rhb said:

Varies. I try to get 3M papers, but I've had problems getting what I wanted.

I recently got 1500-7000 German "Matador" brand paper from LANHU via Amazon and Chinese made 7000-15000 grit paper marked "German Technology" from the same Amazon seller. The Chinese paper appears to be of similar quality to the German.

Click to expand...

Wow. Robin uses 220 grit.

I lapped some carbide pads for a repeat-o-meter yesterday using 240 to 1500 grit diamond plates and then paper to 15000.

This was the first time I tried all the German papers wet. They curled up worse than anything else I've used. Would not stay stuck and curled up into a 1-2" tube when removed. That was a huge disappointment.

The Chinese all behaved flawlessly.

Try lapping film instead. It's on a plastic backing and won't curl when wet.

How the heck do you keep things flat, especially small things, on paper media?
("Shiny" i get)

smt

I'll let you know how flat I got it when I get my sodium vapor lamp and can put a flat on it. In general small things need to be done differently, eg. precision flat Arkansas stone.

Where can I find SiC film in less than 200 sheet packages? I'd never heard of it, but it's clearly what I want for finishing work.

rhb said:

I'll let you know how flat I got it when I get my sodium vapor lamp and can put a flat on it. In general small things need to be done differently, eg. precision flat Arkansas stone.

Where can I find SiC film in less than 200 sheet packages? I'd never heard of it, but it's clearly what I want for finishing work.

Click to expand...

Here's one place:


Ted Pella might have something too, try giving them a call.

Thanks, I'll do that. AO film is easy to find. But not SiC. Diamond is also easy to find, but insanely expensive.

I bought some metal backed diamond laps from Amazon, both grooved and ungrooved. They are made from 1 mm steel sheet. So they *really* need a flat mounting surface. Some 3/8" or 1/2" plate glass should do nicely.

I'd like to note that my "lapping" using SiC paper on a plate has generally been flattening whetstones, washers, etc. All loose tolerance stuff. Lapping a small part would be finished on a flat whetstone, not on sandpaper.

rhb said:

Thanks, I'll do that. AO film is easy to find. But not SiC. Diamond is also easy to find, but insanely expensive.

I bought some metal backed diamond laps from Amazon, both grooved and ungrooved. They are made from 1 mm steel sheet. So they *really* need a flat mounting surface. Some 3/8" or 1/2" plate glass should do nicely.

I'd like to note that my "lapping" using SiC paper on a plate has generally been flattening whetstones, washers, etc. All loose tolerance stuff. Lapping a small part would be finished on a flat whetstone, not on sandpaper.

Click to expand...

That first site has both SiC and AlOx. SiC is pretty expensive too, it's not as common since most use AlOx. You could also try Buehler.

And yeah diamond is off the charts for non-import brand. Even import isn't cheap.

Buy diamond lapping compound in tubes of graded sizes, and roll your own laps.
I make them about 1/4" thick for small laps ( 2" x 3" aprox)
That way you can use copper, soft steel, or CI
Even Aluminum would probably make a good lap from a cutting standpoint, except is it less thermally stable than the others if you will be handling it a lot.

Small dedicated ball bearing on a shank to charge them.
The bort goes a long way. The laps last a long time, too.

Stamp the back of the laps (before final flattening and charging) so you know what grit or color grade they are.

smt