Hi John,

I can see why it was hard to explain in words.

I think the larger holes are for clamp bolts. The one on the left presumably takes a through bolt. the holes look large enough for the clamps to be used when the tailstock is moved some way off dead centre.

The half-threaded hole and slot are clearly for a screw arranegment to allow deleicate adjustment of the offset, and I think the hole on the far side is for a plain bar/pin, in lieu of having guideways.

Similarly, I think the hole at the back is for another pin to make setting in the default centred position easier.

It's clear the offset adjustment is not expected to be very much (say 1/4&quot. All in all a fairly ingenious and easy to manufacture solution, but much more vulnerable to wear than the usual dovetail or tenon arrangement. That said, how often do we offset our tailstocks? – I've only done it about three or four times.

Neil