Half nuts disengage by themselves

My Atlas 1/2nuts always are disconnecting from the drive screw. What should I look at there?

I took mine apart and cleaned it without difficulty. It was very dirty. The carriage clamp bolt just unscrewed, so I bet that you are being blocked by some spooge on the ordinarily unused part of the bolt thread. Do not try to force it, at least not initially. Instead, use a scriber or pick to break the deposits up first. Soaking with acetone also helps a lot, as does ordinary methylene chloride based paint stripper. Once the bulk deposits are removed, a little force is OK - the parts are all made of steel.

I just looked at the manuals for 5900 and 6900 series lathes. The carriage clamps are identical, as shown on page 31 (pdf page 38) of the

Joe Gwinn

First, clean the screw and nuts and associated mechanism. You may need an awl or something to pick the most stubborn bits of swarf out of the teeth. If the half nuts or the cam that engages them are badly worn, there may not be much you can do to help them. If you have a 3/4" leadscrew, replacement parts are available from the Clausing Service Center for what seems a reasonable price. If the leadscrew is bent, it need to be straightened. Also check that the leadscrew is running through the center line of the nuts. if the bed has been ground or something it might be off-center.

My recollection is now hazy, but I seem to recall a detent ball and spring that helps retain the cam and engagement handle in position. So you can check the condition of that.

If the teeth of the nuts are worn very much, they form a ramp that drives the nuts apart. Also, a really badly worn leadscrew can get the same way. The only hope there is replacement.

Jon