Eight Gear Manufacturing Methods: Illustrated Principles

There are various tooth profiles, with the involute profile being the most common. The manufacturing methods for involute profiles generally fall into two categories: the forming method and the generating method.

Let’s take a look at several methods for machining tooth profiles.

Gear Milling

Milling gear teeth using a disc-type module cutter or an end mill is a form-milling process, where the cross-sectional profile of the cutter teeth corresponds to the shape of the gear tooth spaces. This method offers relatively low machining efficiency and precision, making it suitable only for single-piece or small-batch production.

Form Gear Grinding

This is a type of form machining; however, it is less commonly used because the grinding wheel is difficult to dress.

Generating Gear Grinding

The cutting motion in generating gear grinding is similar to that of hobbing. It is a gear-tooth finishing method and is often the only viable finishing option for hardened gears. Generating gear grinding can be performed using a worm-type grinding wheel, a conical grinding wheel, or a dish-shaped grinding wheel.

Gear Hobbing

This is a generating process; its operating principle is analogous to the meshing of a pair of helical gears. The prototype of a gear hob is a helical gear with a large helix angle; because it has very few teeth (usually z=1) and long teeth wrapped around the shaft, it forms a worm with a small lead angle. After slotting and relief grinding, it becomes a hob equipped with cutting edges and relief angles.

Gear Shaving

Gear shaving is a common finishing method for unhardened gear teeth in mass production. It operates on the principle of free meshing between the shaving cutter and the workpiece gear; utilizing the relative sliding between them, fine chips are shaved off the tooth surface to improve surface accuracy. Gear shaving can also produce crowned (barrel-shaped) teeth to optimize the position of the tooth contact area.

Gear Shaping

Gear shaping is another common gear-cutting process based on the generating method, alongside hobbing. During the process, the interaction between the gear shaper cutter and the workpiece mimics the meshing of a pair of cylindrical gears. The reciprocating motion of the cutter serves as the primary cutting motion, while the coordinated rotational motion of the cutter and the workpiece constitutes the feed motion.

Schematic Diagram

Gear Honing

The principle of gear honing is similar to that of gear shaving; the honing tool and the workpiece mesh like a pair of helical gears without backlash. The process involves relative sliding at the meshing point combined with the application of pressure between the tooth surfaces.

Wire-cut EDM (Electrical Discharge Machining)

The principle of gear honing is similar to that of gear shaving; the honing tool and the workpiece mesh like a pair of helical gears without backlash. The process involves relative sliding at the meshing point combined with the application of pressure between the tooth surfaces.