Keys
Functions
Key is the most commonly used machine part. A key joint is a removable joint as shown in Fig.17.1. It goes through the shaft and hub's keyway, joining the shaft with the rotors(gears,pulleys and clutch), transmitting torques.
Types of Keys
Numerous kinds of keys are used to meet various design requirements. Commonly used keys are parallel keys, woodruff keys and gib head keys(see Fig.17.2)
Choosing Dimensions of the Key and Keyway
One usually first selects the type of key and specifications according to the diameter of the axis and relevant design requirements of the standard to be used. The grooves in the shaft and hub into which the key fits form the keyways or key seats. The dimension of the keyway should be determined following relevant standards.
The keyway on the hub is generally machined on a machine with a slotting cutter. The keyway on the shaft is generally machined on a milling machine. The dimension of the keyway coincides with the dimension of the key .The depth of the keyway should be determined according to the relevant standards. The machining method for the keyway and the relevant dimensions are shown in Fig.17.3(a) shows a keyway on a hub, Fig.17.3(b) shows a parallel keyway on a shaft, and Fig.17.3(c) shows a woodruff keyway on a shaft.