Keyway

A keyway is a slot or groove cut into a shaft and its mating part, such as a hub, gear, pulley, or sprocket, to receive a key. The key is a short block of metal that locks the rotating parts together and transmits torque while maintaining the axial position of the hub on the shaft.

In operation, the key sits in matching keyways on the shaft and the hub. Torque is transmitted mainly by shear on the key and by friction between the key and the surrounding keyways. The key also fixes the hub's axial location along the shaft, helping to establish a consistent mechanical relationship between components.

Common forms include rectangular parallel keys, Woodruff keys (a semicircular form), and feather keys (long, narrow keys for high-torque situations). Keyways are typically straight rectangular slots milled or broached into the shaft and the hub, and may be standardized in DIN, ISO, or ANSI specifications to ensure interchangeability and proper fit.

Manufacture and standards: Creating keyways involves milling or broaching. Standard dimensions and fits are published by ISO, DIN, and ANSI, with different grades for shafts and hubs to ensure proper load transfer and ease of assembly.

Applications and considerations: Keyways and keys are common in machinery such as motors, gears, pulleys, and couplings. They provide simple and inexpensive torque transmission but create stress concentrations and potential wear; misalignment or overloading can lead to key or keyway failure. Regular inspection and replacement of worn components are recommended.