I was going to suggest grinding an M3.5 tap to be completely bottoming (no taper at all), then using that to chase the threads above the grub screw. After that, a Torx bit tapped in makes a decent Allen screw extractor.
Mark Rand RTFM
1: drill out threaded portion of hole above grubscrew to major diameter plus a little - thread there is never going to do anything useful 2; remove grubscrew upwards with ground screwdriver or similar technique 3; replace grubscrew with shiny new grubscrew.
ta-daah!
-- Peter Fairbrother
Well I'm glad you figured it out. When the turret on my lathe started acting wrong the machine diagnostics said it was a switch. An inductive proximity switch. I tested it to the best of my abilities and it seemed OK. Nevertheless I found one new old stock online and ordered it. Installing the new switch proved useless. Since figuring out the turret problem a couple other problems have cropped up and both times the problem was not what the control said it was. So far nothing has stumped me for too long which is good because I live on an island and service calls are really spendy. Eric
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