Why is it not recommended to operate a worm gear screw jack using only the handwheel when the stroke is too long?
Nov 06 , 2025
When the stroke of a worm gear screw jack is long, it is not recommended to operate it solely by handwheel. The main reason is the limitation of its structural characteristics and transmission efficiency. Worm gear screw jacks use a worm gear pair and screw drive as their core, achieving linear lifting through rotational motion. While handwheel drive is simple in structure, it presents several disadvantages under long stroke conditions.
First, the efficiency of worm gear drives is relatively low, typically only 30% to 50%. As the lifting stroke increases, the number of screw rotations increases exponentially, making manual operation not only time-consuming but also extremely labor-intensive. Second, prolonged manual rotation leads to significant friction and heat generation between the worm and screw threads, easily damaging the lubricating oil film and accelerating wear, thus shortening the equipment's lifespan. Simultaneously, the self-locking characteristic of the worm gear requires overcoming significant reverse friction during operation, especially when vertically lifting heavy loads, where the handwheel torque is even greater, further increasing the operational difficulty.
Furthermore, during long stroke operation, the screw is prone to deflection, resulting in uneven transmission, unstable manual operation speed, decreased positioning accuracy, and even synchronization deviations. More importantly, under high loads or long strokes, improper operation can cause the handwheel to backlash due to torque reversal, posing a safety risk.
Therefore, for worm gear screw jacks with long strokes, it is generally recommended to use a motor drive or a combination of manual and electric drive to achieve stable, labor-saving, and safe lifting control. This not only improves efficiency and accuracy but also effectively extends the equipment's lifespan.
