Making Gear Cutters

[Penguingeoff]

A bit of basics re Gear cutting.
A Gear Planer uses a cutter essentially a RACK (Straight gear with a 29 degree angle on the form). The one cutter WILL cut ANY number of teeth on a gear.

Using this and borrowing from another idea from years ago (forget where) I made circular cutters (Silver Steel) with grooves of 29 degrees in them. The grooves MUST be spaced out the CIRCULAR pitch of the gear you will cut - ie 8DP gear, the grooves are 0.39269" apart. (Formula is Circular pitch = Pi (3.14159) divided by DP eg 3.14159/8 = 0.39269") .
This is how the spacing for a RACK gear is stepped out.

These cutters WILL NOT cut a TRUE INVOLUTE form, but the gears will mesh with each other. They MIGHT mesh with an existing gear.

Once the grooves are machined in the cutter blank, teeth are gashed, cutter is hardened ready to go. Easy. NOT - spacing of the grooves bloody difficult to get right.
Advantage of all this - is I have quite a few cutters for gears, ranging from 16DP to 0.25 M (Module). ONE cutter for each size. ie 1 16DP cutter CAN cut ALL number of 16DP gears
As an aside I have been cutting gears on Hobs, Planers and Mills for years

Cutter and gear

Cutter with teeth formed and 1 with out teeth

 

[Richard1]

I believe the idea of applying this to model engineering originated with J. A. Radford from New Zealand. His book "Improvements to your lathe"
http://www.camdenmin.co.uk/engineer...ements-accessories-for-your-lathe-p-1564.html
contains details of how to make these cutters. I have the book and the instructions look they should work. I have never tried to make them but many of his other accessories are now fitted to my Super 7 and work very well indeed. The only part where his instructions seem a little incomplete is in hardening the cutters as he is making them out of HSS not silver steel but give no details of hardening. The original articles were published in the Model Engineer between 1967 and 1971.