I have been asked if I will do a ‘gear cutting 101’ for those with little understanding of gearsand gear cutting (I count myself amongst them… ) So I will endeavour to share what I have determined so far.

Gear sizes/measurements come in two flavours (as you might expect) Imperial and Metric. The descriptions for these are:

Involute DP Gear Cutters ( DP standing for Diametral Pitch inch size) These come in two pressure angles 14.5 degrees and 20 degrees

Metric Module (MOD) have a declared pressure angle of 20 degrees.

Each Involute DP or Module set is made up of 8 cutters which perversely, the number for each type is reversed from each other