Pitch, Screw-Thread

the distance between parallel sides of the profiles of two adjacent thread forms measured along the axis. The pitch is usually measured along a line on which the width of the thread forms is equal to the width of the groove. Multiple threads have both a pitch and a lead; the latter is defined as the distance through which the screw is displaced in one full turn in a stationary nut, that is, the pitch of one screw line of the thread. The lead is equal to the product of the screw-thread pitch and the number of starts; for single-start threads the lead is equal to the pitch.