POLYURETHANE???????

[CountryMachinist]

Has anyone had any luck milling polyurethane. If so what endmills, speeds and feeds should I use? This material is very flexible and a pain in my side so far so any suggestions will be greatly appreciated.

[crazy^millman]

Sharp HSS tools were always what I used. Uncoated carbide tools made for cutting Aluminum will do okay as long as they have a sharp non honed edge to remove the sharpness. Some inserts are honed to sharpened them and others meant to knock off the sharp edge so be careful what your getting when it says honed edge because they are change depending on the tool. Depending on the parts Rice Paper Tape and Bondo to support it is one off if production parts then elaborate fixtures were sometimes made to support the parts. 

[Jim at Gentex]

3 hours ago, 5th Axis CGI said:

Sharp HSS tools were always what I used. Uncoated carbide tools made for cutting Aluminum will do okay as long as they have a sharp non honed edge to remove the sharpness.

^^This^^ and generally slower speeds & feeds keep the material from gumming up the tool. 

Use air blast if you have it to blow the chips away from the tool. 

Like any unusual material, trial and error with speeds & feeds, and holding the part firmly may take some time.

We did some milling on polyurethane parts a few years back using 3D printed vacuum fixtures with suction cups to hold the part.  It worked pretty well as I remember, but I did need to work with the speeds and feeds quite a bit to find a happy medium.

Good luck and welcome to the forum!