"Pete Snell" wrote in message
...
Proctologically Violated©® wrote:


2 flute can plunge cut, 4 flute cannot.


Pete,
Not quite correct.
4-flutes come in "center cutting" and non-center-cutting varieties.
Center-cutting 4 flutes plunge readily. May not have quite the chip
ejection as 2 flutes, but they still plunge very well--may have to peck
more.

Yes, I realized I was being pretty general, but most of the general
purpose 4 flutes don't center cut. (or at least they didn't used to. I'm
getting kinda old and haven't had to buy a 4 flute end mill in a
while.....)

Pete

Your comments were quite on target for older end mills, Pete. I recall
when the vast majority of 4 flute end mills not only were not center
cutting, but the center area was totally relieved. When rebuilding such
end mills, the gashing process to restore the rake angle on the ends
eliminates the center area as well. Center cutting 4 flute end mills are
far more difficult to grind than when using the gashing process.

Harold