Hi Julie,
If you Google ‘Mini-Lathe’, or ‘7×10 Lathe’ you will find dozens of sites showing mods for these machines – things like fitting ballraces in the cross-slide, tailstock locks, head bearings, tool blocks, fine feed systems, digital readouts and so on – the list is endless.
You did not say why you want to modify the motor/belt drive – the actual belt drive is fairly robust – I am still using the same belt after about 9 years of fairly solid use. Incidentally, the belt (at least on my machine) is a reinforced toothed belt. However, the motor and control system is something else. John has documented one version of the motor speed control board pretty well in another thread on this site – the version he describes has a nasty habit of destroying its output devices if the motor is stalled, but they can be repaired. There are later boards which can withstand a stalled motor – so far I have come across four different versions. I am half-way through reverse engineering one of these later ones, but it has a low priority for me at the moment. Note these are not different versions of the same board, but substantially different designs. I think it is probably fair to note that the older board type as described by John in this forum is unlikely to be fitted any longer – the newer ‘stall-proof’ boards should be in common use by now.
If you replace the motor (presumably for a larger one), then first you have the option of DC (as standard) or AC. A bigger DC type will require a new controller board able to handle the bigger motor. An AC type (single phase) is very difficult to speed control (which is a desirable feature of the original machine) – to get good speed control, a three-phase motor is preferred, then a VFD can be used, but this is fairly expensive (probably as much as the original lathe for a good system).
The only other way is to use a (single phase) AC motor, and use the traditional method of different size drive pulleys and shift the drive belts – and I think this will be quite difficult to arrange in a reasonable manner on these mini-lathes. The original motor fits in a fairly restricted space, so it is likely that a different motor will need to be mounted on some kind of extension at the rear of the machine – I don’t say any of this is impossible or impractical, just deserving of some thought!
Maybe you can post again and tell us why you want to do it – that way you should get some useful suggestions.
Keith