The present invention provides a multi-mode drive mechanism. The multi-mode drive mechanism may be employed, for example, in a power tool, for driving a chuck supporting an end effector, such as a drill bit or spiral cut bit, for acting on a work surface. For example, when employed in a power tool, the mechanism can generate rotating, reciprocating, or simultaneous rotating and reciprocating motion. Cutting with simultaneous rotational and reciprocating motion lessens the potential for undesired walking or wandering of the cutting bit by actively removing debris from the cut. Additionally, multi-mode drive mechanisms provide increased functionality in a single tool to accommodate a variety of situations and materials. One aspect of the invention provides a multi-mode drive mechanism including: an input shaft, a reciprocating assembly, an output shaft, a reciprocating block, and a shift collar. The input shaft terminates in an input external spur gear.