Abstract: A modular knurling tool is provided having a tool shank defining a first dove-tail connector and having at least one adjustment drive recess. Any selected one of a number of different knurling heads are adjustably connected to the tool shank by a second dove-tail connector, such that with the tool shank mounted in the tool support of a metal working machine, the knurling head is linearly adjustable along an axis that is oriented in normal relation with the longitudinal axis of the tool shank and in normal relation with the axis of the rotating work piece. A threaded adjustment member is positioned with a circular thrust element thereof located in rotatable relation within the adjustment drive recess so that rotation of the threaded adjustment will impart linear adjustment movement to the knurling head relative to the tool shank.