Lathe - lead screw handwheel

 I made a lead screw hand wheel for my mini-lathe a few years ago. It works, but it's generally a bit wobbly because it's fitted to a very short M8 thread on the end of the lead screw.

You can see it here. The plain section is the tail end bearing for the lead screw and that short M8 thread you can see is the thread for the lead screw end float adjustment. It's very short, probably about 10 mm.

What I've decided to do is to replace this section entirely with a much longer piece that carries the bearing and passes much further into the short shaft I have my hand wheel mounted on.

The first step is to part off the old 8mm section and drill out 7.5 mm, reaming for 8 mm.

Next we will let in a short piece of 8 mm round bar into the reamed hole and we'll retain it with high strength Loctite retainer. This would have been very straightforward had the first piece I selected not been 5/16" rather than 8 mm! Measure twice, cut once as they say.

I put a longer thread on the new piece of rod to retain it solidly into my hand wheel axle.

Here it is in place. It's retained by an M4 grub screw into the plain section of shaft at a point where the end float is minimised. Actually there is no end float measurable in the installation at all.

There are a couple of modifications to the old handwheel here that may be obvious or may not. The wheel fitted in the later pictures is much larger than the old one for better control; there is also a small piece of rubber fitted into a 4 mm hole in the axle which provides a bit of extra friction to the graduated collar.

The collar, by the way, is divided into 62. The lead screw is 16 TPI, or alternatively has a pitch of 1/16" or 0.0625". This means that each division of the collar has an error that amounts to 0.0005" per turn.