Analysis and Design of Machine Elements

4 Detachable Fastenings for Shaft and Hub

Nomenclature

b

key width, mm

d

shaft diameter, mm

F

force acting on a key, N

h

key height, mm

L

length of a key, mm

l

working length of a key, mm

T

torque, N mm

σ _p

bearing stress, MPa

[σ _p ]

allowable bearing stress, MPa

τ

shear stress, MPa

[τ]

allowable shear stress, MPa

4.1 Keys

4.1.1 Applications, Characteristics and Structure

When power is to be transmitted to, or supplied from a rotating shaft, it is necessary to attach power transmission elements, such as pulleys, sprockets or gears, to the shaft. The relative rotation between the shaft and the attached elements are prohibited. Detachable retention devices, such as keys, splines and pins, are commonly used to secure the connection between the hub of power transmission elements and the shaft.

Keys are elements enabling transmission of torque and power between power transmitting elements and shafts. A key is first installed into longitudinal groove cut into a shaft, called a keyseat. The hub of a power transmitting element with a similar groove, usually called a keyway or a keyseat, is then slid over the key. The key seats in the groove of the shaft and the hub so that exactly half the height of the key bears on the shaft and the other half bears on the hub [1]. Keys are demountable, facilitating assembly and disassembly ...