How do I straighten Delrin?

I was using a just resharpened end mill. I need to find the SFM for delrin I was 524 SFM. 1000 rpm. Workpeice did not get warm.

Most likely I need to slow it down a bit. Got new materail that the supplier annealed for me, started way over size I now have 2 blocks to size and straight. 2 hours of skim cuts and flipping them over.

Thank You, Randy

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Randy wrote in news: snipped-for-privacy@4ax.com:

I show face milling with a carbide inserted cutter recommended at 650 SFM for a 0.040" DOC, 600 SFM for a 0.150" DOC and 550 SFM for a 0.300" DOC. Feed around 0.005"-0.009" per tooth.

So if you are using carbide you're probably in the ball park. For HSS you'd want to 300-400 SFM with roughly the same feed rates.

Randy wrote in news: snipped-for-privacy@4ax.com:

Randy,

This is probably one of those cases where taking light cuts at light feed rates will make matters worse. Delrin has low thermal conductivity and a high coefficient of expansion. The chip won't carry much of the heat away from the work. I would run closer to 300 SFM take a decent DOC if the set up is rigid and feed closer to 0.010" IPT than 0.005". Use a cold gun if you have one or coolant of it's allowed.

Dan, Thanks for all your help. I actually did this on my manual mill so feed per tooth is an unknown. Second set of bars turned out really good. Cutting the taper I started with 2 cuts at .150 DOC then finished at .075 DOC. No cold gun but I did use an air nozzle to cool it a bit and keep chips clear.

Thank You, Randy

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Randy wrote in news: snipped-for-privacy@4ax.com:

I'm glad it worked out for you.