Spin welders use radial motion and pressure to friction weld plastic part halves. Lower part halves are clamped to the fixed base. Upper part halves are clamped to the upper rotating spindle. Servo drives control upper spindle speed, torque and feed pressure and allow angular control for final part orientation. Like a drill press, spin welders allow economical plastic joining of cylindrical or spherical parts up to 24″ in diameter.