So I did a couple of tests on these cheap cork trivets from Ikea (probably the lowest cork quality in existence…) :
They are 0.4" thick, 7" wide (for scale). I first tried a few random pockets with a 1/4" 2-flute endmill, 20.000RPM, 40ipm, 0.1" depth per pass:
Then tried a 1/8" 2-flute downcut endmill, 20.000RPM, 30ipm, 1/16" depth per pass, 0.2" deep pockets:
Not that it is super interesting, but here are two videos of the 1/4" cut (EDIT: turn down the volume… you have been warned):
The only difficulties I saw were:
- getting sharp edges. Cork by nature is just a bunch of small grains packed together, and sometimes the cutter (or the chips flying away, since I did not use a dustshoe) will tear one of those grains away, rather than slicing into it. The run with the 1/8" downcut is much sharper (which was the intent…downcuts are great to avoid tearout), and the slow feedrate seemed to help, but with a little experimentation I’m sure one could go two or three times faster without any issue. I also could have cut much deeper per pass if needed, cork is so soft it would not make any different (except for chip clearing…but a dust shoe would help there)
- removing the piece from the wasteboard, since I used tape&glue workholding and cork is so bendy that I had to be careful. Other workholding solutions may be more appropriate.
- profile cuts (cutting all the way through the material) would probably need to be overcut to avoid tearout on the bottom surface. Which is not fun with tape&glue workholding.
I’m not sure what your potentials concerns were, but hopefully this sheds a little light on the matter.