UHMW is crazy to machine particularly if your tools are not razor sharp. The chip tends to all stick together into a mass and it brings a whole new meaning to the term burr. UHMW is the poor man's Teflon as they say but best used where you buy slabs of it, saw it up and screw it down and slide things around on it or whatever. It's like cold rolled steel bar stock that is best not machined into lest you find out something about material science you didn't want to know. Chemically, UHMW is closer to PE and we have had applications where you couldn't use Delrin for pH reasons so we used HDPE instead. And HDPE machines perfectly fine, though not as nicely as Delrin. I believe Delrin is stronger but maybe a bit less slippery than HDPE though I haven't looked it up. HDPE is also more recyclable than Delrin so nice that way but if the part is at all complex, Delrin is best.
I just fixed my apple corer by CNC turning a new knob for the top of the handle out of Delrin. I guess it will now run through the dishwasher every time we make apple sauce, so I will finally be able to test this allegation about Delrin not being good at high pH.
