Milling polycarbonate

Make a sandwich is the key, AL on top and below. Then speeds and feeds for AL. HSS works better here.

Karl

Clean all the oil from the tools and fixtures, as polycarb will craze form oil. (Do not use emulsion coolant either.)

Use lots straight tap water as a coolant. Go as fast as you can without the polycarb softening from the heat.

Polycarb can be a bit grabby.

Joe Gwinn

Joe, I have my chip shield made from polycarbonate. It sees plenty of oil, but does not seem to craze?

Window-grade stuff has an anti-scratch coating on it, which may slow things down. Anywhere you've got a hole that's exposed to oil, though, it'll start cracking eventually. Won't be instantaneous. Doesn't necessarily have to be mineral-based oil, either, have a look at how many Stir-Crazies are in the thrift shops without tops, vegetable oil did them in.

Stan

Hmm. Good point. The chip shield on my lathe is none the worse for wear either.

I may be mixing polycarb up with acrylic. Unless the heat of machining allows the oil to get deeper into the material.

I did a little looking: .

It is the acrylic that is so oil sensitive. But still, water is the best coolant.

Joe Gwinn

Lexan is the one that will craze like crazy.

Lexan is a brand name (GE's ?) of polycarbonate. Bob

i just read the rest of your thread...

I didn't mention I run this dry. The AL does two things - holds the Lexan firm for no chipping top and bottom, and its a great heat sink so you don't get any melting.

karl

I have come polycarbonate junk, I will try to machine it today.

Igor,

I've milled plenty of acrylic using the Hansterfer S500 coolant that you have and there has been no crazing in any of it. Some of the parts date back nearly 3 years and I'd guess that would be enough time for crazing to become visible..

Mike, I totally love that coolant. It is the best!

Has yours started to rot or stink yet?

Nope, even the change out that's been drying it in 5-gal bucks for the past few months has no odor. I use de-ionized water to dilute it though, and the lack of minerals may inhibit biological growth.