Hi Dave,
When you say it is not the gibs do you mean that there is still play when the adjusting screws are tight enough to make the slide tight ? Or do you mean that with the screws tight you can still move the slide. Are the adjusting screws grub screws or do they have lock nuts ?
If they are grub screws could there be two grub screws in the hole ? The second one acting as a locking screw. Sorry to just ask questions without giving any possible solutions.

Les.

Edited By Les Jones 1 on 26/04/2013 18:16:29

Dave, do you mean that you can get a 3 thou feeler in along A-A on the side with the gib adjusters in it? The only gap along A-A (on either side) should be that caused by a thin film of oil.

Andy

A post-script:

I find the best way of adjusting gibs is to remove the feedscrew and push the slide to and fro by hand. That way, you get a more sensitive feel for when each adjuster is just beginning to create a bit of drag.

Of course, as soon as you tighten up the lock nut, it pulls the screw back ever so slightly, even though you are using an Allen key to stop it turning. Sometimes, a few repetitions are needed.

Andy

Hi Graham

Interesting to know that a ball bearing will do instead of a proper pressure pad for a lock screw. As the contact between ball and gib is essentially point I'd have expected the action to be more bending the gib rather than pushing it so the effective "brake" area would be very small. I guess that it works because the actual gib movement involved is, probably, around a tenth of a thou or less so there is pretty much no room for the gib to bend or distort. Not sure if I've got the bottle to try it tho'!

Clive

Another five points to add to those already made:

The parting tool should be at right angles to the work, so its sides don't rub as you go in, and it's overhang from the toolholder should be no more than required to get you to the middle of the job.

Nor should the topslide overhang its base; overhang = loss of rigidity.

The tool should be on centre height; if above, any tendency for it to rock down under cutting pressure will cause it to dig in. OK, with experience you might set it a smidgeon above centre, so it dips to centre height.

It helps a lot to have a saddle lock, so the saddle is clamped to the bed. There are designs around on the Web, but a small C cramp can be pressed into service.

Again, it can help to lock up the topslide, on the basis that it is best to lock all slides except the one you are using, which is the cross slide when parting off. My lathe is of similar size to yours, and has four gib adjusters on the top slide. I added a fifth in the middle, with no lock nut, a little lever and a bit of protective brass as per one of Gray's suggestions.

Sixth bonus point: If you are using a brazed carbide parting tool from a set with brightly painted shanks which the vendor of the lathe thought you might find useful, it would probably be best discarded. The cutting edge on those is usually rather broad for a small lathe, and the carbide may be to the special Chinese easy-chip recipe. I had one, and the tip fell off the first time I tried it, because the brazing failed. It was part of a set my brother gave me as a birthday present (came from Machine Mart, I think), so I couldn't complain, though I've had better presents.

Andy

Edited By Andyf on 27/04/2013 18:46:58

Some of my brightly coloured set needed to be milled underneath to give them reasonable angles!

I use them for intractable materials and nothing else.

Neil

G.H.T. also goes on to say that the best solutiopn is to fit a dowel to prevent side to side movement of the gib relative to the slide.

Russell.