I was given an M head with a Rockwell mill I bought, the M head had no
collets. I cut the tang off a MT2 drill to see how it fit (I didn't think it
would) and the MT2 is to small it goes up in the spindle a bit. So it looks
like this is either a BS 7 taper or perhaps a bridgeport taper. So whats the
best way to determine the taper without a bunch of collets to test?