I am assuming this is done with power feed and that the lathe you have uses the leadscrew for this.

Does the ripple spacing match the leadscrew pitch? If so there is a possibility the leadscrew is bent or something connected to it is out of position or badly made. By badly made I mean something like a gear with the bore slightly eccentric. A bent leadscrew should be visible, gearing in the carriage is harder to spot and fix.

If you change the feed rate and the pitch of the ripples change it points to something in the change gears/gearbox.

A bent leadscrew will move a carriage around if the carriage gibs are not set correctly and produce ripples like this but I have had something similar but not feelable from one end of the leadscrew running slightly eccentrically.

Martin c

I have the same problem with my lathe (Warco WM 290V). It appears to be that the lathe tool is moving very slightly into and away from the workpiece, or maybe very slightly up and down.. I have been unable to measure any movement causing the patterning but have concluded it is a problem in the apron. Possibly a gear with eccentric bore as suggested by Martin Connelly. My lathe had the problem from new, but it took me a long time to realise the issue wasn't caused by the lather operator, by which time the lathe was a long way out of guarantee.

Yes, using the fine feed. I have tried every option I can think of to get round the problem but can't seem to make it better – or worse…

Get a spring/firm hold caliper and set it to span across 5 or 10 of those ridges. Now take the caliper and offer it up to the rack teeth and then the leadscrew teeth. See if the grooves match either of them.

Can also be single phase motor related, mine disappeared when I changed over to Tesla power.

If it's not rack and not screw there's not much else it can be.

I have seen a couple of machines of this class (not warco specifically, but same grade of machine) where the tpaer bearings were too tight on the spindle. You coud not get proper adjustment because the bearing would stick then jump with a loud crack when adjusted. They would go from too loose to too tight in one moment. I had to ease the fit of one of them to let the bearing move with a lot less sticktion then they would adjust up just nice.

Have you tried to hand feed at about the same rate that the power feed is working at? That will eliminate the feedscrew issue and may show up any backlash issues in the lathes saddle gibs.

Neil

Whilst checking everything else, do also check the saddle gibs as Neil L hints. I've seen a similar result from a loose saddle 'walking' down the bed, i.e. because it's being pulled from one edge, alternately sticking and slipping at very regular intervals.