Lathe cutting fault finding strange thing happening

[AndyCD]

Have you tested to see if there's any vertical movement on the cutting tool? looks like something you might see if the tool was moving away from the center of the workpiece.

[Nemo1966]

Have you tested to see if there's any vertical movement on the cutting tool? looks like something you might see if the tool was moving away from the center of the workpiece.

Hi, thanks for the reply. Sort of... I can't see any movement as such with a dial gauge, however I perhaps should have mentioned this only happens for the first 40mm (ish) from the chuck face. If I use a thicker bar with a tailstock and make a cut 70mm from the chuck face the cut is as smooth as a babies bottom - which why I was thinking worn ballscrew (coupled with the ballscreww being 5mm and the tramlines also being 5mm.

thanks again for th reply.