Gang hobbing gears Gear milling a pinion

DJC Gears

This page describes the process to create replacement gears for old an antique mechanism in this case an electric fan.

The gears arrive in whatever state from their past life.

Measure and make notes and decide suitable material or use customers choice of material, in this example nylon, less likely to shatter like the original has, the original parts should be kept with the machine to show original manufacturing methods. Also nylon being a little softer can help reduce wear to the antique.
Make an arbor to mount the blanks on the lathe and cnc mill.
Make a flycutter to a reasonable fit in an unworn section of the original gear.

Fan drive gears.
The broken tufnol gear on the left (there are two in the mechanism).
The two left hand white gears are the test pieces made to check and adjust the cnc (center height) and the gcode (depth of cut).
Third gear in the middle gear engaged with the worm fits reasonably so the blanks are then put on the cnc and cut.
In this case they come off the machine with a lot of fur which due to the small size and material needs cleaning under a microscope with a scalpel (there are 4 gears on the right, best two should be the top two when cleaned).
If all gears come out ok then there will be a couple spare for future use.

Fan drive gears.
After cleaning and one gear mounted on the worm ready to post.