On Sunday, April 26, 2015 at 5:18:04 PM UTC-4, MATHSMAN wrote:
I need to cut a square hole through a stainless bolt, using it as a lathe
tool holder.I have drilled bolt no problem with Cobalt drills. Is it now
down to a lot of work with taper files or can I BROACH IT?

Stainless is a bit more difficult to machine than regular steel. It generally needs more clearanaces, slower speeds and heavier cuts. My guess is with a broach made for steel, you are likely to break the broach using it on stainless.

You could kludge up an electric discharge machine. Another guy and I did that a long time ago.

Just did a search on EDM DIY and found a number of sites with info.

Dan