Microscope rack and pinion

[Gerald LeggParticipant @geraldlegg88621]

[Gerald LeggParticipant @geraldlegg88621]

I have a Victorian microscope whose rack and pinion have been abused. The rack is fine but the teeth of the pinion have been virtually stripped. Could anyone make a replacement or suggest a source? The pinion is 6.6mm in diameter with 15 teeth. My lathe is too big (and ex War Department one used to turn artillery shells). Any help would be very gratefully received. Thank you.

Edited By JasonB on 22/03/2018 15:12:52

[Brian WoodParticipant @brianwood45127]

Hello Gerald,

Is this a straight cut or helical pinion? It will make a big difference to finding a volunteer.

Regards

Brian

[Bob StevensonParticipant @bobstevenson13909]

Find a small piece of HSS,..or even silver steel and grind it down until 'perfect' fit in the teeth of pinion………..Put brass rod in lathe and turn down to 6.6,…then mount the tool and use saddle to 'plane' the teeth into the brass…which is relatively easy on brass, but don't take too big cuts………. Use a change wheel/improvised detent on spindle to 'index' 15 divisions

 

Alternatively, try the massive clock sundries catalogues from the usual suspects such as Walsh, Cousins, or Meadows & Passmore They probably have something that will serve or can be adapted

Edited By Bob Stevenson on 22/03/2018 19:15:54

[john carruthersParticipant @johncarruthers46255]

I had to repair one of Flemming's brass microscopes with just this problem.
It was a straight cut rack and the pinion had lost 3 teeth.
I managed to build up the 12 tooth steel pinion with a tiny welding electrode, skimmed it true, then ground a profile tool to cut the teeth with the lathe as a shaper.

Edited By john carruthers on 23/03/2018 08:33:48

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