Glenn,

I cannot help with making a metal nut, but I had a similar problem with the main carriage nut on my Flexispeed. I used polymorph to make a replacement, moulding it around the leadscrew and then shaping it to fit. So far, it is working well. Others have used Delrin to do the same job.

This my original thread, which contains links to the Delrin idea and several thoughts by others on alternatives to polymorph.

Regards,

James.

I would have thought that i can cut you a nut

lets see a diagram first but I should imagine £50-60 will do it in bronze

Just checked the places I bookmarked. Auto motion in stock and Kingston engineering. Bothe list screws plus nuts in various materials.

Aluminium is also a good option, T6 has very good wear properties and is easy to cut

It might be best to ask what degree this excessive back lash is in terms of % rotation ?

John

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Are you sure you mean 15 mm ? One complete turn of a slide dial doesn't usually move the slide that much. That's why I asked in terms of percentage of a turn or fractions eg 1/10, 10% etc.

The reason I asked is that sometimes people expect too much in terms of backlash. One turn of yours would move the slide by 0.1" or circa 2.5mm but best stick to inches if that's what you have. In real terms on a lead screw with that pitch and new parts might give you around 0.010in back lash maybe up to 0.015in measure on the scales.Lathes with far more than that are still usable.

The answer to cope with backlash is to always wind into a cut. That way the back lash is taken out. If for some reason you wind in too far wind out say 1/2 a turn or more and then wind in again to the correct setting. If the nut was well worn say 1/2 turn 0.050in backlash then wind out over a turn and then back in again. Even with that amount of play the lathe is still usable but most people would be thinking maybe it's time to change the nut. Problem though – the lead screw will be worn as well – if you do organise a tight nut some how it will be too tight in places.

There isn't much on the web concerning adjusting gib strips on lathes. Best done with the lead screw out or disconnected and the slide pushed by hand. What's wanted is very slight resistance to movement and no binding due to the oil film breaking down. People use all sorts of oil but some have changed to slideway oil and found it to be better – including me but your gearbox oil is probably suitable.

There is a bit here but a bit myford based as are other bits and pieces on the site which is now archived.

**LINK**

If you still don't get a decent finish it would be best to post some photo's including one of the tool you use.

John

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Edited By John W1 on 17/11/2015 18:09:14

It might be helpful to remember that there are generally two places where backlash will be created. The thread is one, but the other is where the feed screw is located. The nut wears a bit all along but mainly in one section, but the locating bit wears continuously wherever the slide is.

Cheers, Tim

Take apart the compound to extricate the nut, because If its like my 70 year old British lathe the leadscrew is steel and the nut is bronze and extremely worn. On my one, the tops of the visible threads are almost pointed, they are so thin. You can check for this by screwing the compound right out and check its "loose" movement against a fixed position. A clock dial is good for this. Repeat when the compound is screwed right in. These two extreme positions are not often used in daily life so the leadscrew will hardly be worn, but the nut could be be. In mid travel of the compound both components will be worn.

Frank

When the table leadscrew nut stripped on my Dore Westbury mill , i obtained a 1/2 inch x10 tpi second tap and proceeded to tap a scrap bit of bronze to try it out , i found that it took so much force to make it cut even a few mm i was afraid the tap would break , but looking on a forum i saw a guy had used a hot moulding technique using polyacetal plastic to make a new crosslide nut for his lathe with good results and i had a bit of that plastic to hand albeit in bar form , it was easy to tap 35 mm of thread and completed and fitted to the mill works just fine , should cause less wear to the leadscrew as well ,