A Hand Crank Screw Jack, Also Known As A Manual Screw Jack, Hand Wheel Screw Jack, Or Hand Operated Screw Jack

A hand crank screw jack is a type of mechanical jack operated manually by a hand wheel or crank. They are versatile mechanisms suitable for heavy loads, low speeds, and intermittent positioning applications, commonly used in industrial machinery, height-adjustable tables, and construction support. The hand crank screw jack with a self-locking trapezoidal screw is a mechanical actuator designed to hold heavy loads in position without the need for an external brake. This "self-locking" feature occurs because the friction in the trapezoidal threads is high enough to prevent the load from back-driving the screw. Handwheels often used for intermittent positioning applications, cast iron or aluminum handwheels with revolving handles make manual operation convenient. Note that they do not include a brake, so an additional locking mechanism may be needed for jacks that can back-drive.

These manual screw jacks are indispensable for equipment that requires infrequent but highly accurate adjustments. For example: 

Conveyor System Adjustments: Used to lift, lower, or divert conveyor sections to match different production line heights.

Material Handling: Ideal for roll lifts, saw blade tensioning, and welding positioners where a load must be held securely without drifting.

Machine Calibration: Technicians use them to lift and stabilize heavy machinery during maintenance or to align components in automotive assembly lines.