View Full Version : Problems Machining Micarta

12-30-2008, 06:48 PM
I'm trying to make a small housing out of 2 pieces of black linen micarta. I have no problems cutting it to shape and cutting out assorted pockets in it, but I can't seem to get the face cutout to work. The face will get a screen to protect the front of it and I'm trying to make a cut out for it that is roughly 3x3x.050" (but at this point I'll take any reasonable depth that I can cut cleanly)with rounded corners.

I've been trying an assortment of flycutters to make it. It seems to cut cleaner if I cut it faster, but at the same time it seems very prone to burning, but that's not even the big problem. The real issue I'm having is that it appears that the linen in the cutout is separating resulting in an inconsistent depth. I've tried everything from taking a whole .050" pass to making light .005" deep passes (I've also tried .010, .015 and .020" all with slightly different appearing results, but none even near satisfactory).

No matter what I try, I get a pocket with inconsistent depth and appearance. Since the first one was pretty much ruined I tried cutting it up to .100" in small steps and ended up with a cutout that is the right shape but with varying depth from just about 0-.070" in a random pattern (in other words, it's not like one edge is deeper then the rest, it's just different in different places).

I have made sure that the piece is not moving or doing anything weird.

Any ideas how to get a clean/consistent surfacing cut in this stuff?

12-30-2008, 06:53 PM
Have you tried an end mill?

12-30-2008, 07:16 PM
I'd recomend you use a Carbide tipped router cutter as used in a wood router.

Run your spindle at high speed and use a vacuum if you have it available.

12-30-2008, 07:21 PM
Any help here? It seems that there are many grades but others seem to had had quite good success.


Liger Zero
12-30-2008, 07:59 PM
This is a problem machining filled grades of plastics. Sometimes they lay of the filling is going to be just so and you'll get %&(* results until you switch batches. Purely random not much you can do about it.

Of course this is *my* experience, I'd love a workaround if there is one.

Rich Carlstedt
12-30-2008, 10:04 PM
Its abrasive, and I have had no problems with it when using a very sharp cutter.
I would rough with carbide, and then take a .005 or less pass with a new HS endmill
NO Rubbing !

12-30-2008, 10:42 PM
Carbide down spiral router bit is what I use on plastics that tend to de-laminate.It shears downward so your plunge speed will be slower.Quite a few companies sell them.Grizzly,Homedepot,MLCS,MSC etc.


12-30-2008, 11:31 PM
Rich, is it really abrasive? I can't see how, as it is nothing more than linen, in this case, or Kraft paper, and varnish. Linen is not abrasive, nor Kraft paper and I am pretty sure VARNISH is not.

Micarta was developed and trademarked and patented by Westinghouse Electric Company, many, many years ago.

Until the mid 80's, we had Westinghouse Micarta plant 2 miles from me, dedicated to making insulation for us at the main plant in East Pittsburgh, PA, and for sale to other users.

I have a router table top made from 1 3/16 Micarta. Ploughed a 3/4 dado in it for a mitre guage with no problem, except that it DOES stink when you cut it. That is burning varnish, not actually burning, but the powder smells like hell.

Drum sander with same for table, and a few more pieces. No idea what that would cost to buy, today.



12-31-2008, 12:37 AM
Any help here? It seems that there are many grades but others seem to had had quite good success.


I might be missing what you're trying to point out there... I'm seeing a lot of people selling it (If you remember my last thread, it's harder to buy then to find someone that claims to have some), a few people making it and then some people making knife scales out of it. Like I said, I can cleanly cut it, but I don't see anyone in those links trying to surface a good size area.

I need a fairly large radius corner so I've pretty much ruled out an endmill, I'd need a 1.2-1.4" in diameter end mill to have the corner of the cutout end up where I need it.

The cutter in the flycutter is brand new, never used before... sharp.

01-05-2009, 05:04 AM
Well, it ended up being partially the flycutter and partially the toolbit in it. I tried another flycutter in the set and it did the same thing. I even tried touching up the HSS tool with a diamond hone when I noticed that it was dull almost instantly.

Basically, first, the new set of flycutters refuse the hold the tool well, it kept moving around which is why I was getting an uneven depth of cut. Second, the HSS was going dull almost instantly in the stuff, which is what was causing the burning and general messy cutting.

I didn't have appropriate tooling to confirm this, but I managed to rig up a setup with a modified woodworking circle cutter setup to hold a carbide tipped lathe bit that I had sitting around. That gave me a nice, clean cut.