Engaging the thread cutting dial gauge

[Sammo]

I have a Warco GH 1236 Lathe

It has a Thread indicator on the side of the carriage feed box.

This unit can be located onto the side of the feed box in three positions, and each position engages a diffierent diameter worm, onto the lead screw. With the lead screw running at the same speed. The thread indicator revolves at different speeds depending upon the worm engaged.

Does anyone know, if this is to do with different thread forms?
If so could you please tell me, what do the three positions represent?

Thanks
Sam

 

[12bolts]

Hi Sam,
I'm not familiar with your lathe, but when threading, particularly with metric threads you need to use different gear ratios to make the indicator plate rotate at the correct revolutions for some oddball pitches. It may also enable you to switch between metric and imperial threading.

Cheers Phil