Restoring old lathes, backlash in leadscrews

[BillTodd]

As regards backlash adjustment, what do you suggest? the current nut is about 20mm square so I was thinking that a 20mm cylindrical section screwed into the block and locked in place with a small grub screw. It would need to be a fine thread, maybe 20tpi. Not sure I could do that with the changewheels I have today.

Sounds like a good plan to me :)

Can you get at to adjust it in place? (I can just reach the SB adjuster from the back of the crosslide)

An alternative (used on the hardinge) is a brass bar (with the end threaded in place) pressing down on the screw via the nut mounting hole (I'll add a picture later).

[irving2008]

Neat approach there Bill, but sadly the lug on mine goes into a blind hole in the slide and it would involve modification of the slide itself.

I actually measured the screw accurately last night and its actually 7/16" not 3/8", although if I am remanufacturing it makes little difference. What matters is finding some leadscrew of around that size and a matching tap for the nut at a reasonable price.

I have decided that the screwed in section I previously suggested would be hard to manufacture as I have no means to thread it at the moment. So I am going with the split nut and screw idea previously discussed

[ptjw7uk]

Have you considered casting a nut thread using moglice not any idea how much it costs but an idea.
http://www.moglice.com/articles/repl...tethebook.html
(see figure 14)
I suspect you would need a new length of threaded rod to replace the screw.


Peter

[irving2008]

Have you considered casting a nut thread using moglice not any idea how much it costs but an idea.
http://www.moglice.com/articles/repl...tethebook.html
(see figure 14)
I suspect you would need a new length of threaded rod to replace the screw.


Peter

Peter, I've looked at this stuff before, but its hard to get in small quantites. I did wonder about using plastic epoxy metal and packing the nuts, oiling the screw, screwing it in and leave to set... might contain the backlash for a while - worth a try maybe

[irving2008]

Took the other leadscrew (cross-slide) off today. Its identical to the topslide one, although at some time in the past somone has lopped 7/16" off the brass bearing and inserted a (poorly machined) micrometer dial and attempted to solder a pointer (now missing) to the brass sleeve.

I now have everything ordered I need to do this except some 7/16-10 LH leadscrew, wanted to find a UK source as the US source is 10 days shipping and was hoping to make a start this weekend. Kingston Engineering don't go down to 7/16, their smallest is 1/2 but this won't fit through the holes in the slides :sad:

Anyone know of a UK source for 400mm or so 7/16-10 leadscrew? I wanted to go metric but although MD have 10x2D LH at 99p/100mm I cant get a 10x2D LH tap at reasonable cost unless someone has one they can lend me...

[John S]

Order a bit extra and flute it and get it cyanide hardened and use that for a tap.

.

[irving2008]

Order a bit extra and flute it and get it cyanide hardened and use that for a tap.

.

Interesting, I assume that would be OK for brass, being a lot softer (I dont suppose it would tap brass without hardening?)

Where and how much roughly?