Feed & Speed Calculator for Delrin (Acetal / POM)

The failure mode here is melting, not tool wear

Delrin has a low melt point and poor thermal conductivity compared to metal — heat generated at the cutting edge has nowhere to go and builds up fast, and once it gets hot enough the chip stops breaking cleanly and starts smearing and re-welding to the tool and part. A worn edge is rarely the problem; a chip load too light for the speed, generating friction instead of a clean shear, almost always is.

Why low flute count and high chip load work better here

A single or double "O-flute" tool with a large, open flute valley clears chips fast and gives each tooth a bigger, cooler bite — the opposite of what you'd want in steel. Running a high-flute-count metal end mill in Delrin at a metal-appropriate chip load is one of the most common ways to melt a slot instead of cutting it.

Air blast beats flood coolant for most setups

Delrin doesn't need coolant to lubricate the cut the way metal does — a strong air blast to clear chips and carry heat away is usually enough, and avoids the mess and part-marking that flood coolant can cause on plastic. If chips are packing or re-welding, that's a signal to raise chip load or improve chip evacuation, not to add more coolant.