There are many ways to make gears, hobbing is one of the commonly used processes for cutting them from a blank. There is a cutter that looks something like a m

There are many ways to make gears, hobbing is one of the commonly used processes for cutting them from a blank. There is a cutter that looks something like a milling cutter, but it is turned in sync with the gear blank: https://en.wikipedia.org/wiki/Hobbing https://en.wikipedia.org/wiki/Hobbing