I reckon its so you can use a drill where the tang has broken off. It will tend to grip in one direction and release in the other direction, thus allowing the drill to be removed easily, if you use a standard reducer the broken tang drill would be difficult to remove.

I have never seen one of these before, but they look as though they might do the job.

Phil

In theory you should be able to drive it out of the spindle using a standard removal wedge, then as you say, twist the spring to release it from the broken tang drill.

I do agree with you that it is not something I would want in my own spindles.

Phil

Hi guys, such devices are generically called use-em-up sockets, the commonest of which is a forged morse taper with a flat on 1 side of the bore ie it is D shaped, take damaged drill, tidy up broken tang, grind dirty great flat on taper till it will fit in the new socket along its full length, knock it in up to your usual standard of agricultural violence, this is NOT precision engineering, regrind drill point, carry on, quick, cost effective, blah blah.

Bob H.

Looks like it would be cheaper than buying a whole new say 2" diameter drill bit after the tang has been sheared off. They might not bother with getting it off again, just leave it in place?

was it made china