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Cut Off Blade Grinding...?
- Thread starter EmilioG
- Start date
- Joined
- Dec 20, 2012
- Messages
- 9,422
Didn't read this until today. I'm not sure why your washers would warp unless there was excessive heat. Plastics like lower speeds and higher feeds. I don't use UHMW often but I do Delrin all the time and can cut really thin pieces, like 0.010" thick, and have no issues with warping. You might try a lower speed, maybe 100 sfm, and don't dally in the cut. I don't use cutting fluid with plastics as they tend to be self-lubricating. Your tool must be sharp, on center and perpendicular to the work but it should part with little problem. My tools are ground square at the nose, by the way, and leave no nib if I slow the cut as it completes.
Thanks, good to know. I'll do some more experimenting. I have some nylon that seems to machine better than UHMW but its only 1" diameter. I haven't tried parting large diameter thin washers from any other kind of plastic. These UHMW ones were about 2" dia x 0.1" thick & ~0.375 hole which should have helped matters if anything. They were constant thickness & nice finish, but curled slightly. In fact I cranked a heat gun onto one thinking I maybe I could deflect it back but it didn't change much. No way I had anywhere that kind of heat when parting. And when I machined them flat on a plate, they stayed perfectly flat. Weird. Do some plastics have the equivalent of residual stress from extrusion?
- Joined
- Dec 20, 2012
- Messages
- 9,422
In my experience (delrin, polyurethane, nylon), what warps plastic is heat. I suspect anything that is extruded will have some residual stress but I haven't encountered it, sorry. I especially don't expect to see warping with a 0.100" thickness so something weird is going on. Let us know if you figure it out.