Tips for Machining UHMW Plastic needed?

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The title says it all; can you provide me with tips for cutting, turning, boring and milling ultra high molecular weight plastic?
 
I need to make a couple pulleys and chose UHMW to make these out of. I've read online where it requires "special" techniques to machine UHMW and I want to know what these special techniques are. Are there any changes in tool bit geometry, or feeds and speeds, or just what do I need to watch out for?
 
High speed steel tooling with lots of back rake, side rake and clearances, plus and a generous nose radius. Use a cutting speed of around 500 surface feet per minute, slightly higher for finish cuts. The challenging part is clamping the parts without distorting them, so take care with that. Also, be very careful when drilling the stuff because the drill will tend to screw into it. The solution is a rigid set-up in case it happens, and no pilot drills. Just take it out to full diameter in one step. It will also help to knock the sharp edge off the drill with a stone. Also use caution when turning it because the chips will be continuous and love to wrap around whatever they can.

Tom
 
For cutting UHMW use a coarse tooth blade as a fine tooth will gum up with the extra heat. Use coolant while machining because of the low melting point of a lot of plastics. Keep in mind that plastics will expand a lot more than metal, even room temp. will effect size. Main thing with plastic is keep heat away.
Paul
 
Thanks for the information gentlemen, and I probably should have choosen a different plastic but the cost differential really drove my decision.

Thanks Again!
 
Deburring either UHMW or Delrin is a pain, I found a small Shurform file with the file set into the handle to work in the pull position works better than anything else I have found.
 
Froneck said:
I use a sharp "Wirly Gig" Not sure how it's spelled. Sort of a screw driver handle with insert-able blades on the end and made for de-burring. Just about every machine shop supply has them. I think another companies name for it is E-Z-Burr or something like it.

Frank
Click to expand...

I use those as well on plastics, Noga is the brand I believe. They still take a steady hand to keep the tool from digging into the soft plastic. A single edge razor blade works pretty well too.

Tom
 
Frank,

Thanks for your offer Sir, I'll keep that in mind in case what I got does not work out. I ordered a one foot length of 3-1/2" OD round rod and the part I am making is 3.375" OD x 1.000" so I figure I ought to have enough for about ten chances to get one right!

Thanks again!
 
if this is what a customer had to have no change possible
the original guestion is the best method to approach this material
correct?
steve
 
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