I have been having a problem with machining the stop valve spindle for a model beam engine (Mary). This part is stainless steel and is turned down and threaded 12 BA on one end. I know that you shouldn't take too fine a cut on stainless for fear of work hardening so I cut it down to size in one pass - no problem. However tapping it was a different matter: Taps take lots of fine cuts by their nature and the thing seized and broke off in the die. 12 BA dies are expensive and I don't want to risk another one - any advice?
Thanks in advance, Russell.