Abstract: A device which changes rotational movement into reciprocal movement. The device contains a final drive gear and a drive pin is eccentrically mounted on the surface of the final drive gear and is connected to a sliding block, the sliding block is connected to a yoke, the yoke is connected to a slide box, and the slide box is connected to a piston. Needle bearings fit within rounded notches in the outer walls of the yoke and abut with the inner walls of the slide box resulting in a minimum of friction between the yoke and the slide box. Also, a sliding block is present inside the yoke and needle bearings are present between the drive pin and the sliding block and between the sliding block and the yoke to reduce friction between the drive pin and the sliding block and the sliding block and the yoke, respectively.