SCREW JACK Duff-Norton line of screw jacks (mechanical actuators) includes mechanical actuators (machine screw and ball screw) ranging in size from 1/4 ton to 350 tons, stainless steel machine screw actuators, micro-miniature actuators, high duty cycle actuators, motorized machine screw and ball screw actuators, electric cylinders and motor control systems. Accessories include miter gear boxes, c-face motor adapters, limit switches, transducers, visual and digital position indicators, couplings, ball screws and ball screw systems, and locking rings. Screw Jacks are also used for raising and lowering maintenance platforms, opening and closing air dampers, oven doors and sluice gates, and adjusting tooling machine beds, cable tension and workplace tables. In addition to the broad range of applications and industries for mechanical actuators, they are also used as alternatives to hydraulic and pneumatic systems.