In article ,
"Snag" wrote:

They make solid carbide end mills just for such tough materials
. Cobalt EM's too might do the job , I haven't tried mine on that particular
alloy but it worked well on some 4140 I cut recently - I'd go with at least
3/8 or 1/2 inch , low rotation speed and fairly heavy feed with plenty of
coolant .

Aaaand the fundamental difference (which leads to Snag correctly
recommending slow rotation and heavy feed) is that unlike mild steel,
stainless work hardens very significantly. If you "take it easy" and cut
fine shavings you will fail 10 times out of 10. You have to cut serious
chips or not at all. It can be hard to wrap your head around, since the
instinctive response is to back off and go easy since it cuts hard -
that just happens to be exactly wrong for stainless.

Each new cut needs to get "beneath/beyond" the work-hardened "crust" of
the previous cut.

Lubrication was not mentioned - use some.

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