A reciprocating power tool and drive mechanism with a drive shaft mounted for reciprocating movement relative to a housing along a center longitudinal axis of the drive shaft. The drive shaft has a front end adapted to attach to an external shaft or tool attachment, a rear end, and a slot oriented perpendicular to the center longitudinal axis of the drive shaft between the front and rear ends. A motor driven shaft imparts rotary movement to a pinion gear, which meshes with a crown gear to impart rotary motion to the crown gear about its center axis. A drive pin connected to the crown gear has an eccentric pin eccentrically offset relative to the center axis of the crown gear for engagement in the slot of the drive shaft so as to impart the reciprocating movement to the drive shaft on rotation of the crown gear.