Cant seem to get a nice finish

Have a loot at this please

You can see the ripple effect and I can feel it with my finger.

Any suggestion what I am doing wrong?

crossslide adjustment ? Noel.

Are you refering to backlash

Don't think so, are the gibs loose or is the saddle is moving

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

Is the pattern a helix or a series of concentric circles? What type of lathe and tooling?

Andrew

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.

..on closer inspection a redundant comment.. apologies

Edited By DiogenesII on 18/02/2023 19:22:57

Edited By DiogenesII on 18/02/2023 19:25:34

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...

If that was a gear with an eccentric bore you would likely have more pronounced grooves on the half-turn where the gear is binding and less/no grooves on the half-turn where it loses engagement. You grooves look evenly spaced and even depths.

nigel, same lathe as you so same problem

However, cone to think of it it only seems to happen when using the fine feed

What happens to the pattern if you recut it without any adjustments-?(Few times-?)

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.

Try adjusting the headstock bearings a little tighter.

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

I bet it wouldn't do it if you had a three phase motor fitted!

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.

I get a finish like that on my old Drummond M-type when the adjustable tapered bronze headstock bearing bushes need nipping up a bit. Tightening the bearings fixes it every time. (Not that often but have done it several times over the years.)

On a modern taper roller bearing headstock it should be easy enough to measure with a dial indicator reading directly on the spindle or chuck mounting flange. Clamp a piece of bar say 12" long in the chuck and try yanking it up and down on the far end while reading the dial indicator on the spindle or chuck flange. With taper rollers there should be zero movement. Myfords etc with plain bearings, maybe half a thou or so.

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

My first Boxford did the same and I changed bearings and motor without effect.

One day I turned the leadscrew from the rigth end with a monkey wrench and tumbler disconneted,lathe stopped and no cutting.It went very smothly most, of the way and then definately not.By succesive disconnecting the drive train ,the periodic binding was localized to be in the Norton gear box.Taking that appart ,filing a couple of damaged teeth and reassmbling was a nasty job but it fixed the ripples.

I have had same pattern in some of my chineese lathes and I have always localized the problem within a couple of minutes by using hand and brain.