Quote Originally Posted by gatz View Post
did you get the LH screw from Aliexpress ?
Yes, eventually. That purchase turned out to be a non-pleasant experience.

Firstly, I was hit for local tax and customs duty which doubled the overall price. TNT entered a price which was hiked up so the tax was more that it should have been. Since then I have heard that stuff shipped with TNT is more likely to have this problem. Of course they act as the customs agent and charge an additional fee. My thoughts did run to wondering whether this was a nice little earner for TNT.

Secondly, the screw does not appear to be of the same quality as the RH screw which I had fitted previously. The surfaces of the nut were ground much rougher and the action was not very smooth. I decided not to risk fitting it. It resides on the shelf in its shipping box.

That finally convinced me that the best solution was to motorise the fitted screw and drive it with an MPG in manual mode and have a powered mode which would maintain constant surface speed when facing (within the range of speeds of the VFD/motor combination). To that end I bought a closed loop stepper motor and tested a bread board lash up. That worked so well that i decided to fit a ball screw to the Z axis as well. Of course that has to be motorised because ball screws do not come with half nuts. You cannot easily disconnect the feed for manual. Anyway as of today I am waiting for that ball screw to arrive, it should have been here nearly 2 weeks ago. Not knowing what torque would be necessary to drive the screw under the hardest conditions I got a large closed loop NEMA34 motor. Almost certainly overkill.

When this is complete the lathe will be fitted with all the hardware and motor drivers necessary to be a CNC lathe. I do not want a CNC lathe. Every time that I want to turn a simple bush or similar I do not want to wait for a computer to boot up and nor do I want to have to write some G-code or do a drawing to make a simple part. I almost never make drawings. I have analysed what I want a lathe to do and it comes down to:
1. Simple turning and boring.
2. As 1. but with tapers.
3. Facing - preferably with near constant cutting speed.
4. External and internal threading.
5. Ball turning.

I have no need to make fancy chess pieces nor other fancy shapes.
Many people make ELS (electronic lead screw) conversions but most are Z axis only and so will only be capable of 1. and 4. above. Having motors on both Z and X axes allows for all the needs above and the control is still pretty simple. A few calculations of the computing requirements showed that the maximum pulse rate from an Arduino would be inadequate for high feeds at high spindle speeds so I have opted for an ESP32 to handle the smarts. Many times faster than an Arduino and dual core. The two cores allow the motor signals and operator input to be separated.
I have the software written and I am just waiting for the Z screw to get it done.

This started out to be a single sentence reply, but like the lathe itself it has been subject to mission creep.