Cutting Polycarbonate

[Matt Meiser]

I need to cut some 4" wide by 1/4" thick polycarbonate that McMaster Carr has on the way to me for a guard on my crosscut sled. Can I safely cut it with my SCMS and a standard blade? It's hardness is listed as "R118-R126" but I thought RC was the normal "Units" on hardness so maybe this is a different scale? That seems REALLY hard.

[Robert Reece]

You can cut it, but it tends to melt and just gum everything up. The tablesaw seems to work best for me.

I had a negative rake blade on my slide miter and it did not like polycarb at all.

For some reason though, it countersinks very nicely.

[Matt Meiser]

If only I had a finished crosscut sled. :)

[Marty Paulus]

Matt, It is suggested to use a TCG style blade if you insist on using a power saw. Here is more information then you will ever need:
http://distributionbizwiz.wordpress.com/2007/08/22/machining-forming-polycarbonate/.

I have seen some people use a torch to gently heat the cut edge to make it as clear as the face if you really want to take things to the next level! :D

[Glen Butler]

I have cut poly carb on the table saw and the miter saw with out incident. I wouldn't fret too much about it. It is very shatter resistent but at the speed which a blade turns it can shatter, so feed slow and you'll be fine.

[ken gibbs]

Polycabonate will melt when you cut it. Suggest you use a hand saw.

[John Coloccia]

re: Rockwell scales

There's a bunch of different Rockwell Scales.... A,B,C etc. Without giving the specific scale (RA, RC), you just have to guess what they mean.

The Rockwell scale depends on applying a load to an "indenter" on the material you're testing, and then measuring the dent you leave. The details of which indenter you use and the force you apply changes from scale to scale, though. So for example, it would be typical for polycarbonate to be given a Rockwell M scale rating, which uses a 1/4" steel ball and 100kg of pressure for the load. The typical plane iron, on the other hand, is given in Rockwell C scale, which uses 150kg of pressure with a hard, diamond cone for the indenter. You can see that the two scales are pretty unrelated to each other other than the name and the test methodology.

Anyhow, I use polycarbonate for making master templates, and I cut it without any trouble on my bandsaw. Then I clean up the edges by filing and scraping with whatever is handy. Sometimes I even just use a nice sharp chisel as a scraper. It files very well, and actually sands pretty well too if you can stand the stink (I can't, and I don't know that it doesn't release bad stuff). This is mainly why I use it for patterns. Machines very easily and there's no grain or inconsistencies to screw me up when I'm trying to make a master template. If you really really need the edges to be clear, as someone else mentioned you can flame polish it. Micromesh will also get you there. It's pretty common to micromesh an airplane windshield to restore it, for example, and they even sell kits to do it.

[Joe Kieve]

I have cut "Lexan" polycarbonate a number times on a table saw. It has a tendency to ride up on the saw blade unless it is very sharp. It is also prone to kickback. So use some type hold down device to keep it flat on the table and you should be fine. Just be careful and wear safety glasses.

joe

[Glen Butler]

I have not had it melt. When cutting it, the more teeth the better.

[Lee Schierer]

I've found that keeping the blade very low works best when cutting polycarbonate. I generally have 1/4" or less of the teeth showing above the top surface. You will need to use hold downs to insure the plastic doesn't climb up the blade. A high blade will tend to cause a lot of chatter and can potentially shatter the piece.

[Bruce Page]

I have cut a lot of ½” poly with a standard 40 tooth ATB blade on my unisaw without any problem. I found that a moderately fast feed rate works best, i.e. don’t let the material dwell on the blade.