A clutch mechanism, for use in a rotary power tool having a motor, comprises an input member to which torque from the motor is transferred and an output member co- rotatable with the input member, the output member defining a rotational axis. The clutch mechanism further comprises a cam surface formed on one of the input member or the output member and a compression spring carried by the other of the input member or the output member for co-rotation therewith. The clutch mechanism also comprises a follower having a circular cross-sectional shape biased against the cam surface by the compression spring. In response to relative rotation between the input member and the output member, the cam surface displaces the follower along a line of action coaxial or parallel with the spring. The line of action does not intersect the rotational axis.