Hello Richard,

I was fortunate to work a brand new HLV lathe. for 7 years, but that was 40 years ago now, so my memory is not so good. There is a round knob near the rear of the headstock which will select the threading box. The quadrant on the outside of the box is only used for Imperial and special threads, like DP or Mod or additional Metric not covered by the box.

One point to make when setting up for threading is to set your speed first. Increasing the speed alters the trip point on the screwcutting clutch. It is all to do with moments of inertia.

From what I recall there is a sizeable two speed motor on this lathe. In use it is possible to go from high range directly to low range, this might cause some invertors a problem. I know of one person who used a rotary phase converter.

Is your machine fitted with a handle to alter the variable speed, or does it have a separate motor like the one I worked on. If so I suspect this motor will need to be accounted for with the sizing of any invertor. Plus there is the variable DC power feed to the carriage for normal self acting feeds, this too will be a load on the invertor. No doubt the more knowledgeable electrical Forum members can help there.

Regards

Gray,

I have a HLV which is approaching total restoration.

By rear gearbox do you mean the end section which is accessible by opening the end cover? If so, you need to put the gear selector in the end slot and fit the appropriate gears on the banjo then adjust the banjo so that tge gears mesh to complete the train. If you do that, the screw should turn..

On my lathe there is a rod that pokes out whenever you're using the built-in gear cluster which prevents you from swinging the banjo into engagement, so that you cannot run two ratios at the same time and crash the gearbox.

I'm in North Kent. You'd be welcome to come and have a look around it some day Richard.

I removed the motor from mine and fitted a new Siemens 3-phase motor and VFD. The original dual-speed one could have been powered on one speed with a VFD because it had separate windings for the two speeds, but I have the same now with a brand new motor and VFD for high/low RPM rather than a 63yr old motor with wiring complications. I've often see it quoted that the original was super-smooth and supremely balanced, but that was when it was new, and the vari-speed pulleys not worn, the belts not hardened with time. Most good quality new motors will turn the spindle just as smoothly, or at least not any less smoothly that you could tell.