This recommended practice defines a method for measuring worn fillet roadside fit involute splines. This concept for measuring worn splines provides a direct wear depth dimension by utilizing the unworn involute surface as a contact point from which to measure the depth of wear on the spline tooth at the pitch diameter. Fig. 1 shows spline wear patterns and pitch diameter gaging points. Gages encompassing this concept would basically consist of fixed and movable probes which contact the unworn involute surface known as the form clearance and the worn surface at the pitch diameter thus providing a direct wear reading which is reflected on a dial indicator. Refer to paragraphs 4 and 5 in Fig. 2.