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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.
Motorized Performance



Motorized Actuator Performance


  • Actuator speed reducer drive motor and limit switch in one package
  • Machine screw and ball screw actuator models
  • 2-ton through 35-ton actuator capacity
  • Increased load capability over previously supplied motorized actuators
  • Allows one, two or three actuators to be driven with one motor and speed reducer
  • Four standard speed reduction ratios
  • Consult factory for other ratios
  • Top and bottom screw stops to prevent accidental overtravel (slave actuators do not have screw stops).
  • Equipped with 1750 RPM, 230/460 volt, 3 phase motors. Consult factory for motors with other speeds, voltages and features.


To Order Motorized Actuators, Specify the Following:

  • Actuator Model
  • Translating or rotating screw version
  • Upright or inverted configuration
  • Type of screw end (translating screw actuators)
  • Travel
  • With or without boot
  • With or without anti-backlash feature (machine screw actuators)
  • With or without internal keying (translating machine screw actuators)
  • With or without limit switch (and mounting position if with limit switch)
  • Position indication (visual or digital) -if required
  • Speed reducer ratio
  • Motor horsepower
  • Brake motor standard for ball screw actuators.
  • Specify if brake motor is required for machine screw actuators.
  • Side and position for speed reducer mounting
  • Duty cycle parameters (application load, frequency of use, travel, etc.)
  • For other requirements consult factory