Just an anecdote (1) - Shifters

I'm trying not to criticise another's working memories, but production turners most likely did a 5 year apprenticeship and were working a heavy industrial ( and therefore more stable) machine. I don't think any turner that I've worked with and I've worked with some pretty tasty ones, could cut an 1'' Acme thread to a good standard of accuracy in four cuts. Acme threads are a precision thread used for such things as machine lead screws, where minimal play between the screw and nut is paramount, making it one of the most difficult threads to cut. A skilled turner, in my experience, would use two tools, a roughing tool and a finishing tool to produce the thread form. The roughing tool would cut a few thou below the root diameter, while the finishing tool would cut both flanks together, while not removing any material from the base of the thread, therefore avoiding any juddering which would effect the accuracy of the two flanks, and yes, I've cut my fair share of Acme and buttress threads. An Acme thread cut in four passes would, in my opinion, be only suitable for something like the screw for a sash cramp, where play between the screw and nut is desirable. To compare a hobby machinist to an industrial machinist is not a fair comparison, to a hobby machinist, time is not the over riding consideration, as he or she does it for the sheer pleasure and satisfaction of producing a machined component in his, or her spare time, a process that might be light years removed from his, or hers every day working life.

There is a clear relationship between the horsepower of the lathe and the rate of metal removal. Big lathe=bigger cuts

Neil