Page 210 - Gear Technology Solutions

45° is a popular pressure angle for splines which also indicates that the result
of measurement and calculation is realistic. It is recommended that the major
diameter of the sprocket is equal to the outside diameter of the spline shaft to
assure a major diameter fit. If the sprocket is the transmission output of a uni-
directional unit, then the flanks can receive a small backlash (e.g. sprocket
spline tooth thickness tolerance ISO 7H and shaft spline tooth thickness toler-
ance 7f). If sprocket and spline have to transmit torque in frequently changing
direction, then a transition fit or a press fit of the spline teeth is recommended
(sprocket ISO 7H, shaft ISO 7n.

The tolerance of the major diameter of the internal spline should be a selected
as a transition fit for example ISO H7 (the outside diameter of the spline shaft
should be ISO j7).

14.5 Defining the Cutting Tool and the Cutting Parameters

The tool for the spline shaft can be a standard ISO spline hob cutter module
2.0 with a pressure angle of 45° and sharp corners at the hob teeth. Due to the
profile shift of xExternal = +0.572, the hob cutter has to be retracted from the the-
oretical position by xExternal*m = 1.144mm away from the shaft.

The tool for the internal spline can be a standard ISO spline shaper cutter for
example with 8 teeth. The center distance between shaper cutter and internal
spline is:

Center Distance = d0/2–x*m–d0Cutter/2
= 24.00/2–(–0.572)*2.00–(d0Cutter/2+m*xt)

A profile shift of the shaper cutter xt might be required with the low number of
cutter teeth and is therefore considered in the center distance formula.

14.6 Summary

This article provides a guideline for the selection of a suitable standard in con-
nection with the kind of spline to be designed and manufactured. Some basic
formulae have been explained together with a strategy for how to find standard
tooling by calculating an appropriate profile shift factor for the spline to be de-
signed. If an aftermarket part like a sprocket should be matched to an existing
spline shaft, then the dimensions of major and minor diameter can be found on
the shaft. Addendum and dedendum have to consider the recommended top
root clearance (on the not centering top root combination). If those facts are all
taken into consideration, then it is not important to know if the mating existing

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