I think I have discovered the cause of at least some of the 'mashed' gears I have had to fix. All the broken gear teeth have been replaced by screw studs filed to a fair profile which seem to mesh OK without any 'clunks'. Well, my MARS lathe restoration project has progressed to the point where it is operational and being used for some 'real' work (as distinct from producing some replacement parts for itself). The final picture is of the lathe overall in its current state. Next I started on the feed screw drive train which also has a gear with a couple of broken teeth. The fourth picture shows roughly how they should mesh. Need to consider whether, for the sake of three missing teeth it might be better to build up replacement teeth rather than strip off all the good teeth and shrink on the ring for re-cutting. The rebate to the root of the teeth is 5mm, so there is only 6.5mm of 'meat' under the teeth. The overall height from the rebate to the top of the teeth is 11.5mm.

I did some measuring to determine the available metal on the damaged bull gear. If left it soaking on the parts washer until next week. We were reluctant to apply too much more pressure for fear of damaging either the gear or the spindle. We put it in to 20 tonne press and took it up to 2 tonnes. It is keyed to the spindle and positioned against a shoulder on the short (LH) end, so there's a long piece of shaft along which it must be extracted. With a lot of care most of it came apart pretty easily until I got to the bull gear with the broken teeth. The last two Tuesdays I have been concentrating on dismantling the headstock spindle and cleaning all the parts. Not major problems as everything is keyed and I can ensure they are tight when reassembling. The grub screw fixing the clutch fork in the gear change spindle was loose.

The only issues arising were that the 3-step pulley had one grub-screw missing and the other one was loose. Fortunately we have a hydraulic press so not an insurmountable problem. It was a bit of a struggle removing the input shaft due to burrs caused by the grub screw fixing the 3-step pulley. It just looks like the results of normal wear over many years but I decided I should clean the whole thing out as part of the project. They're fine, and the oil looked OK but there a bit of sludge in the bottom with very fine metal powder. I noticed that there was a lot of play between the input and output shafts of the gearbox so thought I had better check it out to check that all the gear teeth are OK. There's a 3-step pulley as well as a 2-speed gearbox on the overhead shaft arrangement, so there's plenty of speed options. Another half-day working on the MARS lathe today.

Cleaning atlas lathe parts