Ext metric thread cutting, 1124 kerry lathe.

[rossi46]

Hi, diyer novice. Threading constantly starts a new thread. Tried leaving half nut engaged and disconnecting pulling out x slide cranking back.
Can only produce a good thread form by stopping on the clutch then pullig back xslide, disengaging chuck speed gear, manually reversing chuck, with half nut engaged. Back at start, re engage chuck gear return xslide, add compound cut, and so on.
Anyone give some clues.
Cant see any excessive wear and thrust backlash minimal.
Mike

 

[john.k]

I think you will find the half nuts and /or leadscrew are worn/damaged (assuming backlash is taking up).........backlash has no effect ,provided you let it take up before the cut starts.

 

[rossi46]

I think you will find the half nuts and /or leadscrew are worn/damaged (assuming backlash is taking up).........backlash has no effect ,provided you let it take up before the cut starts.

Cheers John,
Yes, i run passed the workpiece start, so as i begin new run thr blash is consumed.
Why would this then still occur and why does it appear to work when i reverse the drive
I am thinking of adding a fwd,stip, rev switch to automate the process, but should i need toi?

 

[john.k]

I would check the half nuts for swarf accumulation in the grooves first.

 

[rossi46]

Cheers