AGMA 18FTM01 PDF

International spline standards such as ISO 4156, ISO 14, ANSI B92.2, and SAE J499a have detailed definition of 2-dimensional spline geometry but cover only the most basic axial effects such as helix error. Other widely used published documents, such as those written by Dudley, and Cedoz & Chaplin, provide information about stresses, including some axial effects such as misalignment. Many recent studies of load distribution have been published, but a general approach is not defined. Even armed with all these documents the engineer is not provided with adequate guidance regarding several factors that influence how a splined interface functions. Additionally, for some characteristics small diameter spline interfaces behave very differently from larger diameter splines.

This paper presents information that is not found – or is not satisfactorily covered – in current standards and existing papers. These include: how to calculate the effective pressure angle of straight sided splines that is needed to accurately determine normal and radial loads; how to calculate the effective centering force of a spline pair; an update to the Dudley misalignment factors that can be applied to splines of any size; and an update to the calculation of the maximum axial force that a spline can transmit via friction.

Results from analytical studies of centering forces and misalignment factors are provided, and an experimental study of centering force is discussed.

The effective pressure angle calculation method is based on the tooth thickness and profile angle and can be included in future standards and guidelines. The centering force analysis is supported by results from prior published measurement data (Medina, Olver) and new measurements. The misalignment factors are an update to the published table (Dudley) that covers a very limited – and undefined – spline size range. The friction force calculation method is a correction to widely published (Maag, and others) formulae that do not include the cam effect of normal force.