Sunday and I am working the afternoon. First job was remove a couple of broken screws from a BSA Air rifle. The screws had snapped off flush and needed removing so they could be replaced.
In the old days I would have used an Easyout which is basically a tapered coarse threaded left hand tap. Drill a hole in the offending stud/screw and screw the Easyout in, being a left hand thread it should, in theory remove the broken screw. The downside is they do not work particularly well in shallow screws, plus the small diameter versions can be incredibly fragile and if you snap one off in the stuck screw you have a real problem as you will never drill the broken part out.
A good alternative are the flat taper sided extractors from Wilde Tools, same principle plus you can give them a gentle tap to start them and I have never snapped one yet however I do have a few gaps in the sizes I hold.
Then there is always the old school (Shudder) approach of hammering a file tang into the drilled hole however the tangs should not really be hard enough for this application, also it is not an ideal solution for small screws, so what does this leave us?
Well believe it or not, I use long series Milwaukee Torx bits that are designed for an impact driver. They are incredibly tough, the multiple parallel splines spread the load and they are also sensibly priced, not that I have ever had to replace one.
The process is very simple, centre punch the end of the broken screw, in this case drill a 2,5mm hole and I always use Guhring Cobalt drills for such jobs. Carefully tap the correct sized Torx bit into the hole, it does not need to go in too deep and you need to take care not to expand the diameter of the broken screw causing it to jam. Finally, unscrew the broken section of screw and it really is as easy as that for the smaller screws, these were M5.
…and why am I telling you this? Because you need to know.