Â* I ended up using my one homemade indexable end mill , only took 2
triangular inserts . What worked was to lock the rotary table in
position and using the end of the mill to do the cutting . Average depth
of cut was around .015" per pass , cranking slow in X . I first tried
locking down both axes and advancing the RT one hole (in a 47 hole
plate) at a time . That calculated out to about .003" feed per hole .
Full depth cuts , and that didn't work so well . I didn't make a killin'
on this , but learned a little more about machining hard materials . I
gotta say , I felt very pessimistic about this whole thing when an M42
end mill just skated on the part . Delivered them today and found out it
took 20 years to cause the damage , this should give him 20 more - and
this was their only option , parts are no longer available .

--
Snag
Yes , I'm old
and crochety .
Get off my lawn !