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14 Design Parameters for Splined Connections

14.1 What Standards are used to Define the Spline Geometry?

Splines are machine elements which connect a shaft with a rotor. Next to
transmitting torque the spline might be utilized in addition to centering the rotor
to the shaft. It is interesting that the splines tooth profiles are involute, although
the involute profile does not contribute to the torque transmission, nor is it
linked to the centering function. The reason for the involute profile is the fact
that most external splines are manufactured by hobbing with a standard
straight sided symmetric hob tooth profile, which is fast and delivers good ac-
curacy results. The internal spline has to be manufactured with shaping or
broaching, using an involute cutting tooth profile. The nomenclature and pa-
rameters of a typical spline connection are presented in Figure 1. The spline
connection in Figure 1 is neither centered on the flanks nor on its major or mi-
nor diameters.

Figure 1: Design parameters for splines

The exception to the involute profiles is the parallel straight profile spline which
requires a planning operation for the external member and a single tooth shap-
ing or broaching of the internal member. Splines can be organized into 2 main

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