Feed & Speed Calculator for Delrin (Acetal / POM)
Delrin cuts easily and takes almost no force — the real challenge is heat, not the material fighting the tool.
Delrin / acetal starting ranges
| Tool | Cutting speed (SFM) | Chip load, 1/4" single/double-flute (in) |
|---|---|---|
| Carbide, sharp/polished flute | 500–1000 | 0.004–0.008 |
| HSS | 200–400 | 0.003–0.006 |
Low flute counts (1–2 flute "O-flute" style) with generous chip clearance work better than high-flute-count metal-cutting tools.
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.