15.87mm, is, of course, exactly 5/8”🙂. ‘About’ may not be near enough but about 0.1mm is neither here nor there for the diameter of a leadscrew.

The 'normal' first recourse for this problem is to turn the leadscrew end for end and use the 'back' face that hasn't been worn much. You have to make new ends of course.

I'm not sure if people are appreciating the advantage for lathes moving from square thread to Acme/Trap with a sloping face. The half nuts can be made with deeper threads firstly to give space for crud but so that the nut engagement can be increased with wear (the grub screws mentioned on the other thread) and adjusted to reduce backlash. If the thread bottoms out on the leadscrew the nuts can be bored out a bit as they should be considered sacrificial. You need to do the adjustment sufficiently often to avoid wearing a ridge on the nuts.

So al in all you haven't got a problem, you just need the right approach.

Looking at the other thread on ML10 Leadscrews, it sounds as if a Metric Leadscrew for a ML might be be REAL hybrid.

Possibly made from the same raw material as for an Imperial machine (Makes sense, or they would have to make the mating bearings/ couplings Metric as well, in a smaller volume )

So it could be 3 mm pitch ACME form Leadscrew made out of 5/8" bar!

Curiouser and curiouser?

A bit like my mini lathe, with a 1.5mm Leadscrew but 20 tpi Leadscrews on the Cross and Top Slides!  But the DROs can accommodate that  

Howard

Edited By Howard Lewis on 15/03/2020 15:15:04

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Good summary here: **LINK**

So Why Use Acme Threads…What is it All About?

They also have numbers, and printable thread gauges !

MichaelG.

Do you really need a new screw? Unless you are milling in the lathe backlash doesn't matter. The only time you need a thread particularly accurate is if you are milling in the lathe for which you could set up a DTI, or for making new cross slide screws or other tool screws for which you can use the unworn backside of the existing screw cutting in reverse.
A lathe can only make a new screw slightly shorter than its own leadscrew without some complications.
If you are making a screw and the nut it doesn't matter whether they are Acme, Trapezoidal or muggins own brand as they can be made to match. If buying a nut all you had to do was ask the vendor what angle it was. If the vendor doesn't know do you really want to buy.
If getting one made don't forget to tell them to use imperial stock or the super high quality nut might not fit.
If you have access to another longer newer lathe you can true up the existing screw by shaving off the unworn sections – nothing says the peaks and valleys have to be the same width and it only matters when you have repeatedly done this exercise taking the metal down to about half a mm or too thin to do the shaving 'cos it bends away from the cutter.

Paul, did you get anywhere with sourcing any leadscrew material? I also have a similar problem with a worn but still useable leadscrew on my speed 10. Ive been looking for tr16 x 3 LH screw material but having no luck. I appreciate the suspicion the tread may well be metric acme but I was going to give trapezoidal a shot.