Tips for Machining UHMW Plastic needed?

[Topos]

I've cut tons of the stuff. What do you want to know?

Frank

Along this line would you have direction in shaping strips of 1/4 " lucite strips
into a semi-circle?

Task is to make a curved back to replace thin backing in a 30 year old Knoll Secretary
chair.

Thanks.

 

[Bill Gruby]

This will tell you what the basics are for bending Lucite. Frank, a hair dryer will not get hot fast enough. I have tried it. I bend a lot of this stuff in model building. You need a heat gun.

http://www.ultimatehandyman.org/video/acrylic/bend.php

"Billy G" )

We are drifting away from the original post a little. Let's try to stay focused on "Machining UHMW"

 

[Tom Griffin]

Along this line would you have direction in shaping strips of 1/4 " lucite strips
into a semi-circle?

Task is to make a curved back to replace thin backing in a 30 year old Knoll Secretary
chair.

Thanks.

You'll need to get it over 300F to make it soft enough to form, so an oven or a number of heat lamps will probably be necessary. Once soft, it can be formed over a wooden form. There is an easier way to do it though. Since Lexan (poloycarbonate) can be formed cold, get a sheet of that and roll the curve in it before cutting the strips. It would be a lot less work than heating and forming individual strips of acrylic. All you need to do is find someone with some slip rolls to form it.

Tom

 

[dirtyjim]

i'll give you a couple tips i picked up years ago working in a plastic machine shop. if your trying to machine uhmw tubing instead of solid rod cut a piece of 1/2" or 3/8 plywood to the same as the i.d. then put in in the end that you clamp in the chuck, all our machines were also fitted wityh 6 jaw chucks.
you'll want to use very sharp hs tools and the trick to parting it off is you must pull the shaving or it will bunch up on top of your partoff tool and break it.
the best way to get a hold of the shaving it to lay your left thumb on top of the partoff tool right before it starts to cut. this will cause the shaving to bunch up on the pad of your thumb where you can easily grab it, then start pulling it out as it cuts.
i would stop trying to part them off at least 2" away from the chuck.