A motion conversion assembly is provided, wich is adapted to be attached to a power drill for converting rotational motion of the drill to a reciprocating motion to operate as a reciprocating saw. The motion conversion assembly is mounted in a housing, and employs an offset-angled spindle on a rotatable drive shaft which is coupled to an intermediate shaft sub-assembly in the housing, which cooperated whith the offset-angled apindle to produce a reciprocating motion in the intermediate shaft subassembly as the rotatable drive shaft is rotated.