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Make a spur gear to match existing rack

Greybeard UK

Jan 7, 2024
Hi Guys: Looking for some advice on making a new spur gear to match an existing rack on a rather old machine.
The rack is cut into the Z axis column on a small vintage Westbury mill. See picture with dodgy looking worn 20T brass gear (it occasionally jumps teeth)
Rack has pitch of 0.125". Pressure angle is 20°. Looking at calculations I've found on internet, CP = 0.125"; DP = 3.142/0.125 = 25.136.
Module = 25.4/DP = 25.136. So Module is very close to 1.
Can I get away with using a Module 1 gear cutter?

Any advice appreciated.


  • rack and pinion.jpg
    rack and pinion.jpg
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