Definition of screw jack

A screw jack is a metal support post that operates by turning a leadscrew and has all its components (rotating shaft, output linear motion shaft or a screw and support bearings) integrated in a housing. Screw jacks are used for lifting, levelling or positioning heavy equipment or for supporting structures and are being operational with the help of a screw or hydraulic cylinder and piston. They can be powered mechanically, electrically, manually, pneumatically etc.

• Ball screw jacks - which use recirculating ball bearings on a precision pitch screw for lifting. These types of screw jacks are needed especially when long duty cycle or high efficiency applications;
• Machine screw jacks - which use screws with less pitch and usually do not have ball bearings. They are less efficient than ball screw jacks, but have a higher resistance at back driving and vibration;
• Roller screw jacks - are a derivation from ball screw jacks, therefore they have high efficiency, but use threaded rollers instead of balls. Overall, they are used in applications that require strict load capacity, speed, axial stiffness, acceleration or deceleration.

• Bell-bottom screw jacks - operate by the same principle as a threaded nut and screw, which makes them extremely helpful when it comes to lifting high loads (up to 24 tons in large models);
• Ratchet jacks - were widely used in mines, shipyards or railroads; these jacks are built to hold round lever bars and usually designed for general use;
• Hydraulic jacks - are compact and suitable for working in tight places;
• Post jacks - are suitable for light-duty applications and consist of two metal pipes sleeved one into another and topped with a manual screw.

Advantages of using screw jack

• self-locking (when the rotational force on the screw is removed, the position will remain the same as it was left before it stopped rotating,,this is machine screw jack's featue);
• safe;
• they create strong bonding and are resistant when it comes to losing the material they connect with;
• resistant to rust;
• specifically designed to be used on wood, sheet metal, concrete, drywall etc.

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