Like gears, splined shafts are used to transmit torque. However, they are so different from gears that it is impossible to duplicate any of their function.
Following are some of the unique features of a splined shaft:
Splined shaft transmits torque using all its teeth
A splined shaft uses all its ridges or teeth to transfer rotary motion, unlike gears that use only one or two of the gear’s teeth. For this reason, they effectively transfer torque in rotary drive applications or acts as a linear guide when used with bushings or bearings with internal splines.
Splined shafts are externally machined
The gear’s teeth can be externally or internally machined. But that’s not the case with splined shafts. Since its purpose is to mate with its female version, a splined shaft is always designed to be the male version and thus their teeth or ridges are externally machined.
The difference between external splines and internal splines
During the application, the external splines of a male shaft mate with its female version having the same number of ridges or teeth or internal splines. In other words, external splines belong to the drive shaft while internal splines belong to its mating component like a female-splined bore or gear.
The different types of splines
Splines come in different type each having a unique physical profile and differs in how they transmit torque:
Parallel key splines have teeth or ridges with a square profile
Involute splines have tapered ridges that decrease stress concentration
Crowned splines have modified teeth that taper towards the end face to allow for angular misalignment
Spline serrations have angled teeth allowing for more teeth on a smaller diameter shaft
Helical splines are ridges forming a helix pattern about the shaft
Without a doubt, splined shafts are necessary because of their unique qualities and how effective they are in transmitting torque.
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