Back to Richard’s problem, which is he doesn’t have a functioning lathe yet!
I’d start with a thorough inspection. Good to be sure before wasting time and money that there isn’t a sinister reason it’s in that state! Are the bearings worn or seized? Does the bed dip near the chuck due to wear? Are the lead-screw and half-nut in good order? What’s missing or broken?
Armed with a full list, try to cost it, time and money. Severe wear and too many damaged/missing parts is probably a showstopper. Spares are almost impossible to find, so have to be made. The broken countershaft is easily fixed by welding, or maybe brazing. But only if the necessary tools and skills are available! Likewise, change gears can be 3D-printed, but CAD-skills and a 3D-printer will be needed. Do you have a workshop or friends? Watch out for the distinct possibility that the cost of repairing the machine exceeds the cost of a second-hand lathe in good nick or buying a new one.
Sinister reason: the lathe wore out in the past, was cannibalised for spares, and then left to rust in hope it might be useful.
Before starting, decide what you want to achieve. Some possibilities:
- You enjoy repairing old gear and see this as a learning opportunity. That’s OK
- You want to become a skilled machinist. A bad way to start because the lathe has to be fixed first, and it could be “Beyond Economic Repair” or the faults get in the way! (Much easier to learn on machines in good condition than wonky ones.)
- You want to fulfil a project by cutting metal. Doubly not OK, because nothing happens until the lathe is fixed and you’ve learned how to drive it. Also, if projects are the goal, make sure the lathe does what’s needed. For example, threading might be important. Most model engineers own screw-cutting lathes even though small threads are mostly made with taps and dies.
- Trying to save money by fixing up an old banger, DIY. Not OK if the cost exceeds buying a good one, or restoring it takes too long!
Picking on threading if it is needed, then an ELS is probably the best answer. And, in simpler form it will do plain turning too. The Flexispeed had a non-standard substitute for change-gears, and replacing it’s patent mechanism feels tricky unless someone else has plans. They may not exist.
Driving the lead-screw with a stepper motor makes good sense, it’s simpler. I’m not worried about Bazyle’s dislike of ELS on reliability grounds. His concern doesn’t apply unless you have a strong need for a system that lasts decades, in which case a lathe in this condition doesn’t auger well for reliability! An ELS may be the quickest and easiest answer, and not difficult to replace if it breaks later. Ironically, Bazyle worries about the perceived unreliability of electronics when this lathe’s mechanical drive is a dud! Anyway, Bazyle and I are presenting considerations not black and white alternatives. It’s down to the owner to decide what’s important to him: reliability or simplicity?
What sort of work is the lathe for? Knowing that steers Richard’s approach. That and the art of the possible!
Dave