I was able to use a file to start removing the "mushrooming" and ended up using the dremel to speed things up. So I don't think it's hardened. A bit of history, the pin GM# 590832 has been in use for various applications since 1939 and is described as 1/4" tapered x 11/16.
The lock pin in the SP250-50B Small parts kit is 11/16 long (.688 ) and measures .249" on the small end and .254" on the big end. So yes, its slightly tapered. I can "scratch" it with my old timer pocket knife blade so its not very hard.
I have close friend with a Bridgeport , along with a shop full of metalworking equipment, and I'll see if I can't talk him into getting the case squared up on an angle plate and get it drilled out with some level of precision.
