Thread: Working with acrylic?

I just got an order of stuff from Masecraft and Phil was kind enough to throw in some samples. I have some red silk acrylic slabs that I was thinking about using and wanted to know if finishing them are the same as working with Micarta or G10. Shape, sand, sand, sand, buff, polish.

Can I use the same speed with my buffer or will that generate too much heat? I'd hate to get through all the sanding to melt or blister something that is close to being done.

Take a little piece that you haven't worked on and experiment to find what works best for you and your equipment. That way you won't be ruining anything if you burn/melt it.

It's a good practice to establish boundaries this way when working with new materials.

Pretty much the same process but acrylic is more delicate & easily scratched compared to G10 etc. Don't need much pressure at all to get results. Find your feet with a sample as Alex said.

Agree with the above. Do not use a colored buffing compound it can melt into the acrylic. Red rouge is especially notorious for this.Too high speed and or too much pressure will do you in. Softly softly. The acrylic also will scrape easily with a square edged tool to make the contour. The back of an Xacto knife for instance.
~Richard

I don't know if this is common knowledge.

My father is a instrument mechanic (CNC, lathe, ect.) at Aarhus university and when they drill holes in polymers they use a "negative" drill bit. Practically it's an ordinary drill bit where you flatten the cutting edge. This should lead to easier control when drilling and smoother holes.

When I was working as a plastics fabricator we would flatten the cutting edge of the drill bit on a bench grinder. Of coarse pretty much the same effect can be obtained by drilling into concrete and bluntening the bit. The reason a blunt drill bit is used on acrylic is to stop it biting into the material and cracking it. This is however more of a problem with larger holes, I've never had much problem drilling a 1/16 size hole with a sharp drill bit. Still a good idea though.
Grant

The trouble with blunting a drill bit is that a small flexible drill bit may wander. For acrylics, a blunt/dull drill would generate a great deal more heat which will give a snot ball on the drill, and a much larger than desired hole. A blunting process for a 1/16th drill is more than my old eyes can handle.

I have found running a drill motor at low speed and using a bit of saliva or dish soap on the tip of the drill bit, plus drilling a bit and pecking it into and out of the material to allow both to cool may give the best results. "Slowly, slowly, catchee monkey"

There are also "for plastic" drill bits. They are made with a very sharp tip having an included angle of less than ~90º. Normally they are sold by plastic supply companies. Most places selling them by mail order have a $25 US minimum order. If the plastics sheet supplier is in your city, they often have a showroom/over the counter sales room.
Plastic drill bits, one source:
Plexi-Point drill bits for drilling in plastic from FTM, Inc. - The Fabricators' Source

Cheers
~Richard

I agree Baldy, with small holes it is probably not an issue.

However, the "snotball" effect in polymers has in my opinion very little do do with the sharpness of the bit. Instead, it is a strong indicator that you are going too fast. If it where metals I would totally agree that a dull bit would result in significantly higher temperature.

Also, the wandering is easily avoided with a small centre-punch.

Generally with polymers, go slow. The melting point is often pretty low (100*C), although for acrylics, I think it's 150-200*C.