Sorry about the misunderstanding.

Mine does exactly the same sort of thing, but once it is in use, it performs perfectly. I reckon I am well within 0.01mm, which is good enough for anyone except the purist.

Just one problem with them, when used with an RT with a chuck fitted, you very quickly run out of throat room. I have made some shorter probes which gives me about another 25mm or so to play with. They don't need to be super accurate as long as the touch point is nice and smooth when it is in use, it only ever uses a tiny portion of the probe tip, not the full circumference.

BTW, they are very good to use on the lathe as well, as a quickie check to see if your tailstock is in alignment. But you must first check to see that your chuck has zero runout.

Bogs