On Mon, 14 Nov 2011 08:08:05 -0800 (PST), Searcher7
wrote:

On Nov 14, 10:39*am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, *etc.).

I assume that as long as melting your way through the stock is not an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.

Greetings Darren,
I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and
Acetron for example) will release formaldehyde gas when heated too
much. This gas is corrisive as well as stinky and poisonous. Acetron
can be knurled with standard bump knurls. It deforms remarkably well.
Different plastics require different coolants. Water for acrylics,
soluble oil for nylon, uhmw, acetal. The oil does stick to the
plastics but comes off with the proper soaps. Oil must be kept away
from acrylic. It will cause cracks. The cracks may not show for hours
or days, or maybe not until the plastic is stressed. Sharp positive
rake tools work best for most plastics. Nylon absorbs water so if it's
going to be used as a water lubricated bearing it should be roughed
and then soaked in water a couple days before finish machining.
ERic

Thanks everyone.

I'm working on quite of few projects involving plastics and I guess my
biggest concern was gumming up my metal working tools.

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.

Darren Harris
Staten Island, New York.
That slot will be easy. You can probably get away with just an air
blast to remove the chips and keep things cool. To insure a good
finish and accurate size use an undersized endmill, 5/32 would be
good, and climb cut both sides of the slot instead of just plunging in
with a 3/16 cutter. But at such a shallow depth you might get away
with 1 pass with a 3/16 cutter. Just make sure you use a sharp cutter.
To help with getting a good finish on the bottom of the slot stone a
small radius on the sharp corners of a new endmill. .005 radius is
adequate. Can your slots have a small radius in the corners? If you
use a brand new cutter with sharp corners the bottom of the slot may
end up kind of furry.
ERic