Page 51 - Mechanical Engineer's Data Handbook

40 MECHANICAL ENGINEER’S DATA HANDBOOK

I .6.3 Strength of keys and splines

A key is used to prevent a machine part from moving
relative to another part. In the case of a shaft, the key
must be strong enough to transmit a high torque and is
often made of alloy or high tensile steel. The fit may be
either ‘close’ or ‘free’ if sliding is desired. The ‘keyway’
in the shaft and hub is usually produced by milling. Saddle key

mkzl

Gbhead T Rectangular
Round key

Splines are a means of keying a hub to a shaft where
b-width
h-depth separate keys are not required. They consist of mating
L - length 450,. s
S - chamfer &w grooves in hub and shaft of rectangular, triangular or
involute form. The grooves are designed to allow axial
sliding.
FeaMer

Internal External involute

Triangular Square
Gib head Feather Rectangular Splines
Key applications

Types of key

The main types of key are the _ectang~--.r’ where the
keyways are half the key depth, the ‘feather’ where the
keyway is closed at each end, the ‘Gib-head’ used
always at the end of a shaft and with a head so that it
can be tapped into place, the ‘Woodruff key’ which is
segmental and for use on tapered shafts, and the
inexpensive ‘saddle’ and ‘round’ keys.