Abstract: An improved reciprocating saw is designed to compensate for distortion in a reciprocating blade head due to tensioning of a blade pack. The saw incorporates an improved linear rail pair supporting the blade head via four bearing housings. A first pair of bearing mounts which compensate for rotary motion between the blade head and the bearing housings are attached between a respective pair of the bearing housings and one side of the blade head a first blade head side member. A second pair of bearing mounts which compensate for both rotary motion and linear motion between the blade head and the bearing housings are attached between a second respective pair of the bearing housings and the opposite side of the blade head. The inventive bearing mounts thus compensate for bowing of side members of the blade head during blade tensioning.