The screw jack, also referred to as 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 excess weight by the thread self-locking function, and the structure is simple, but the transmission effectiveness is low and the come back 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 normally released, the weight can be quickly lowered by itself and the return time can be shortened, but the framework of the jack is usually complicated. The screw jack can support heavy items for a long period, and the maximum lifting capacity has Conveyor Chain reached 100 tons, which is trusted. After the horizontal screw is usually mounted on the low part, the weight could be traversed at a small distance.
Principle of use:
The mechanical jack is one of the types of manual lifting tools. Its compact framework makes reasonable utilization of the rocking of the rocker to rotate the pinion. It really is operated by a pair of conical gears to drive the screw to rotate and force the lifting sleeve so that the weight rises or decline.
Instructions:
1. Before use, it is necessary to check if the jack is normal, whether the components are flexible, add lubricating oil, and properly estimate the pounds of the large object. Use a jack of suitable tonnage and steer clear of overloading.
2. Adjust the technique of supporting the teeth on the rocker. Firstly, turn the rocker directly in the clockwise path by hand to help make the lifting sleeve quickly ascend the top weight.
3. Insert the handle into the rocker hole, move the handle along, and the weight will rise. When the reddish warning line shows up on the lifting sleeve, the handle should be stopped immediately. If you want to lower the teeth in the contrary direction, the pounds will begin to fall.
Precautions:
1. Often keep the surface of the machine clean, check the internal structure regularly, make the pinion in the rocker versatile and reliable, and lift the lifting sleeve freely.
2. The friction surface between your lifting sleeve and the casing must be oiled anytime. Other oil filling holes ought to be lubricated regularly.
3. In order to consider the safety used, avoid overloading, work with illness, it isn’t appropriate to make use of multiple units to avoid danger.