When the rake angle of forming gear cutter is 0, the tooth profile of this cutter is the same as the groove shape on the end face of spur gear (see figure). There are mainly four kinds of forming gear cutters. ① Disc gear milling cutter: used for machining straight or helical cylindrical gears in single piece, small batch or repair production. ② Finger gear milling cutter: used for machining straight teeth, helical teeth and herringbone gears with large modulus. ③ Gear broaching: it is often used to process internal gears in mass production. ④ Gear shaper cutter head: it is mainly used for machining spur external meshing cylindrical gears under mass production conditions. When machining a helical gear with a disc or finger gear milling cutter, the shape of the normal section of the gear is slightly different from that of the cutter tooth profile. The shape of any tooth is not cut by one cutter tooth, but is cut by several cutter teeth.
Generating gear cutter When the generating gear cutter is used to process gears, the gear to be processed and the cutter rotate respectively according to the required transmission speed ratio, and the tooth profile of each adjacent cutter is continuously enveloped into the tooth profile of the gear. This kind of cutter is often used as gear hob, gear shaper cutter, gear comb cutter and gear shaving cutter, and is used to process all kinds of involute gears with straight teeth and helical teeth, arc gears with non-involute teeth and cycloidal gears. When machining involute gears, generating gear cutters are more general than forming gear cutters. For example, involute gears with the same modulus and pressure angle but different teeth numbers can be machined with the same tool, and modified gears with different modification coefficients can also be machined with standard gear hobs. In addition, generating gear cutter has high machining accuracy and productivity, so it is widely used in production.