I recently did a job where I had to turn, drill , bore, and part off some rollers that were made out of uhmw. The uhmw was white (if it makes any difference)and it was a solid 3in. dia. bar. Anyway, I had a problem with the parts growing in size after they were out of the machine. I would check the bore dia. while it was in the machine and it would be right (1.848 dia.), but as soon as it was parted off it expanded about .003 Now here is where it gets weird. The parts would continue to expand about another .007 over the course of several hours.
I made sure all the tools were sharp, and I used the coolant on each operation. The chuck pressure was at 150 lbs.
Any guesses about why the parts got bigger?
Thanks so much.