Wolf Jahn Cross Slide Tool Post Question

[rodabod]

Hi,

Has anyone seen a tool post mount like the one on my Wolf Jahn slide rest?

It has a conventional slot on one half, but the other half has a plain face with four screw holes. Could this be for attaching a vertical slide? 

I’m wondering if I should machine a square with a conventional slot and screw this down so that I can attach my tool holder closer to to the work (and thus reduce tool chatter). 

Also, does anyone know what screw sizes thy used on German lathes? The screw sizes are 3.2mm and 3.5mm and the thread pitch is 0.725mm, so neither Metric nor BA or Thury  

Thanks. 

[vinn3]

those are not watch tools.

[rodabod]

41 minutes ago, vinn3 said:

those are not watch tools.

Do you mean the slide rest? It’s a Geneva pattern Wolf Jahn which was part of a 6mm Wolf Jahn set. 

[measuretwice]

I don't think you have room to machine a square/slot etc - it looks like the top of the milled surface is the underside of the t slot overhang.  So what about making two strips the right width and thickness and with countersunk screws fasten them into the existing threaded holes....sort adding back what was milled away?

Edited February 14, 2018 by measuretwice

[rodabod]

5 hours ago, measuretwice said:

I don't think you have room to machine a square/slot etc - it looks like the top of the milled surface is the underside of the t slot overhang.  So what about making two strips the right width and thickness and with countersunk screws fasten them into the existing threaded holes....sort adding back what was milled away?

I think you are probably spot-on. I asked an engineer about this today who also suggested that the original slot may have been milled off. 

I wonder if someone else previously fitted a tool post where those four screw holes are. I can’t find correct screws to fit the existing holes, so was considering re-tapping to M4. 

I can screw down a square section of 3mm gauge plate and then mill a slot to match the existing slot exactly. 

Thanks for your advice. 

[rodabod]

Plate fitted. Working well now.