Surface fitting of an involute spur gear tooth flank roughness measurement to its nominal shape

•A numerical rigid body motion is applied to topographies.•Topographies are relocated on spur gear teeth numerically.•The spur gear nominal geometry is subtracted from topographies.•Artificial examples show the method’s effectiveness.•Real gear measurements show the method’s effectiveness.

A method for fitting a topography measured on an involute spur gear tooth flank to its nominal shape is proposed, so that the exact position along the length of the tooth from which the measured surface originates can be determined, and so that the nominal shape of the surface can be subtracted prior to roughness parameters calculation.