"DoN. Nichols" wrote in message
...
In article ,
snip-.

Of course, none of my milling machines have such an index pin,
because one uses 30 taper, one uses 40 taper, and one uses ER
double-angle collets, none of which have such key slots.

It's been years since I last ran a mill with a 50 taper, but I recall that
even they have keys, only in this case they are drive keys. Large mills
are capable of turning large cutters, so they can easily overcome the taper
drive. The #50's with which I was familiar were used in spindles on
Cincinnati, Van Norman and K&T mills. The shoulder at the large end of the
taper had opposing slots that accepted hardened drive keys that were a part
of the spindle. Do your holders have such slots?

Harold