The screw jack, also called the mechanical jack, is driven by a manpower through a screw pair, and a screw or nut sleeve can be used as a jacking member. The ordinary screw jack supports the pounds by the thread self-locking function, and the structure is simple, however the transmission performance is definitely low and the return stroke is slow. The thread of the self-propelled screw jack does not have any self-locking action and is equipped with a brake. When the brake is usually released, the weight could be quickly lowered by itself and the return period can be shortened, however the framework of the jack is normally complicated. The screw jack can support heavy items for a long time, and the utmost lifting capacity has already reached 100 tons, which is trusted. After the horizontal screw is normally mounted on the lower part, the weight could be traversed at a small distance.
Principle useful:
The mechanical jack is among the types of manual lifting tools. Its compact framework makes reasonable utilization of the rocking of the rocker to rotate the pinion. It is operated by a pair of conical gears to drive the screw to rotate and drive the lifting sleeve so that the weight rises or decline.
Instructions:
1. Before use, it is necessary to check whether the jack is regular, whether the components are flexible, increase lubricating oil, and correctly estimate the excess weight of the heavy object. Use a jack of suitable tonnage and avoid overloading.
2. Adjust the technique of supporting one’s teeth on the rocker. Firstly, turn the rocker directly in the clockwise path by hand to make the lifting sleeve quickly ascend the top weight.
3. Insert the handle in to the rocker hole, move the deal with up and down, and the excess weight will rise. When the red warning line shows up on the lifting sleeve, the handle should be stopped instantly. If you want to lower the teeth in the opposite direction, the excess weight will start to fall.
Precautions:
1. Always keep the top of machine clean, check the internal structure regularly, make the pinion in the rocker flexible and dependable, and lift the lifting sleeve openly.
2. The friction Conveyor Chains surface between the lifting sleeve and the housing must be oiled anytime. Other essential oil filling holes ought to be lubricated regularly.
3. To be able to consider the security used, avoid overloading, use illness, it isn’t appropriate to make use of multiple units 
to avoid danger.