Hob

http://en.wikipedia.org/wiki/Hobbing

This article is intended to go with Involute Gear

The process of cutting a gear calls for either an involute cutter or a gear hob. The advantage of a hob is that it can easily be cut from carbon or tool steel on a lathe and milling machine. Once cut, the hob is then heat treated (even mildly will suffice) so that it can more easily cut the gear material. There are a few types of hobs, namely helical and what I will, for lack of machining experience, call a parallel hob. Out of simplicity, this article will focus on the so-called 'parallel hob' as it can be used on a standard vertical mill and doesn't require a hobbing mill.