A mechanized sexual stimulation device is provided that provides a reciprocating stimulation body, preferably emulating a male in function with various length of penetration possible. Designs herein allow the protruding dildo to move back and forth to a variety of length, speeds and angles while flexing in many directions. The device includes a housing with a ball reverse screw rotatably mounted to the housing, and a reversing nut which retains bearing balls that allow the nut to move linearly up and down the ball reverse screw as the screw is turned in a single direction, thereby moving a reciprocating stimulation body such as a dildo connected (indirectly or directly) to the reversing nut. Channel or groove structures on the ball reverse screw and reversing nut guide the reciprocating back and forth stoke in a linear motion.