Kip, while I've seen references elsewhere to line boring I don't have the facilities to do that. And I'm sure the old-timers didnt go to that lengths. Also I don't see how you'd ensure the mandrel was aligned correctly with the tailstock if its just a short length of plaster.

Anyway I've found a local company in Watford that'll regrind the shaft by 4thou to bring it parallel and they quoted me £35 so hopefully I'll get that done this week and try again next weekend. I got some 2mm sheet ally and cut with my hole-saws two 2" washers with 1.25" centres and then took a 6mm hole in the top of each to act as air vents. This should be less likely to blow out. I'll seal the edges with fire-cement and clamp them across the bearing with a couple of small G-clamps.

In the meantime I've swapped out the 1.1hp 1-phase Atlas motor I had for a 1.5hp AEI (c1965) 3-phase with a Jaguar VXS-75 VFD courtesy of eBay (£75 the pair, bargain). I've also cleaned up and rewired the 0.5hp motor that came with the 3.5" Gamages lathe. This motor is proudly labelled 'The British Thompson-Houston Motor Co Ltd' and is very British in its heavy cast iron casing and gloss black finish. BTH became AEI in 1959 (and then were taken over by GEC in '67) but this motor dates from the late 40s or maybe early 50's and runs beautifully and silently.