leinin sliderest

Looking at Lathes.co.uk they show handwheels with 80 divisions, that would equate to M5 x 0.8 which is standard metric coarse. Though if they have used a trapezoidal form and the standard pitch of tr5 is 1.0mm 

Have you put a DTI against the slide to see how far it moves with one turn of the handwheel and what divisions on the handwheel?

Edited By JasonB on 20/09/2018 20:56:35

M5 x 0.8 seems entirely logical, Jason

Apart from the Pultra and the Jason, none of my 'watchmaker' lathes has feedscrews

As ever: If Lee could post a detail photo of an unworn section of the thread, I would be happy to try 'measuring' it.

MichaelG.

.

http://www.lathes.co.uk/leinenmodern/

Edited By Michael Gilligan on 21/09/2018 08:11:49

Would that be using your ipad "measure" app

.

The App that I use for these remote efforts is called 'EP Calipers'

MichaelG.

.

P.S. "Optical Metrology" is not to be sneered at

Edited By Michael Gilligan on 21/09/2018 08:27:24

From the photo Michael posted it does not look like anything special just a Vee form standard metric thread.

Can you post a decent closeup photo of yours

.

But can you take a decent close-up photo of your thread ?

MichaelG.

.

Did you notice the echo, Jason ?

Edited By Michael Gilligan on 21/09/2018 20:30:12

.

We're really into guesswork now Lee; but I suggest you try [gently] a 2BA screw for size.

The BA threads were based on a Swiss thread in the first place; so it's not as improbable as you might think.

MichaelG.

.

https://en.wikipedia.org/wiki/British_Association_screw_threads

.

Edit: Sorry ... I've just re-read your opening post, and you state that  it's not BA

Edited By Michael Gilligan on 23/09/2018 06:54:53

I see a new one has 1.0mm pitch and 100divisions, as you say ave a word with Boley to see if they can help, may even sell spare nuts.

Could be Lowenherz thread as the 5mm dia one is 0.8pitch, 53.8deg

Edited By JasonB on 23/09/2018 07:12:21

Jason,

Sorry to correct you, but Lowenherz threads were 53 degrees and 8 minutes, not 53.8 degrees

They were used by German and Austrian instrument makers into the early 20th Century so that thread form is a possibility. I imagine taps/dies to suit are now unobtainable.

Perhaps Lee's best hope is to hot form a nut in Delrin from his thread and use that, suitably machined, to make a new feed nut

Brian

There is no reason to suppose they would use a standard thread, it's not like they are going to make the leadscrew from a bit of allthread from the hardware store. More likely they thought of the pitch they wanted to use and the diameter that would be suitable and made them in-house. Making a suitable tap would be trivial for a machine tool maker.

As well as trying an M5 nut did you try a screw in the feednut? It may be that it is close to standard M5 but depth or crest height is different, or it is the angle that is different in the way that UNC and Whitworth fit in one combination but not the other.

Very handy Michael, not seen that app before.

If you are going down that route then think about getting a tr5 leadscrew and matching nut which would retain your dial readings and be the ideal thread form.