Trevor
That sounds very wrong. The Dickson T2 or S2 is pretty much the standard QC post for Colchester Students and Masters.
Normally fitting just requires a T shape spacer/washer on top to take up the difference between the stud diameter and the QC post bore. Supplied in official kits. Maybe a longer stud too if the toolpost is deeper than the standard four way but I thought that was only necessary if the taller T2T version of the Dickson was used which was always a pointless exercise as the increased height is of no benefit. Unless you just happen to have a T2T and didn't feel like shelling out for an ordinary one!
If I were making mounting gear from scratch I'd make the Tee nut longer so it pulls up over the whole base with of the post but, realistically, that is coming over all Inspector Meticulous.
Looking at Tonys Lathe.co website he shows a version of the topslide with the Tee slot at 45° rather than straight across carrying an American style lantern toolpost, third picture down on this page **LINK** . Something I've never seen, nor has anyone else I've mentioned it to, and always felt was an American affectation for the Clausing-Colchester version. If you have got one of those I guess the top slide will have to be tapped in the middle for a fixed, screwed in, stud as done on many other lathes.
Clive
Edited By Clive Foster on 22/08/2020 11:10:18