Generative Methods of Gear Teeth Cutting

There are many gear cutting processes at the makers disposal, but every process is a compromise between ease of use, good surface finish, profile accuracy, speed of output and economic production. 'Perfect' profiles and finishes are not obtainable by normal industrial processes due to minute ridges and scratches caused by tool shapes or the motion of rotary cutters.

Generative Methods: The most common and popular gear machining processes in use today fall under this category, including hobbing, shaping, planning and gear rack cutting. These processes generate the gear teeth as a result of relative motion between the gear blank and the cutter.

In this process, the gear blank is fed into a machined cutter that reciprocates or rotates against the gear blank to cut teeth. This process is a highly efficient and productive gear machining procedure, however, it has a number of disadvantages.

First, the gear blank needs to be made with a proper dummy on one side, so it can support the work-piece during the machining operation. Thin and wide gears are not suitable for this process, as they cannot be held properly on tapered arbors.

Second, the dividing head used in this process needs to be correctly set up so that the gear blank fits perfectly on it. This is done by ensuring that the gear blank has a diameter that is as large as the outside diameter of the gear it will be fitted to, as this is the reference point for the cutter to work from.