The screw jack, also known as the mechanical jack, is driven by a manpower through a screw pair, and a screw or nut Cast Iron sleeve is utilized as a jacking member. The normal screw jack supports the weight by the thread self-locking function, and the framework is simple, however the transmission performance is usually low and the return stroke is sluggish. The thread of the self-propelled screw jack has no self-locking action and is equipped with a brake. When the brake can be released, the weight can be quickly lowered alone and the return time can be shortened, but the structure of the jack is definitely complicated. The screw jack can support heavy items for a long time, and the utmost lifting capacity has reached 100 tons, which is trusted. After the horizontal screw is definitely mounted on the low part, the weight could be traversed at a little distance.
Principle of use:
The mechanical jack is one of the types of manual lifting tools. Its compact structure makes reasonable use of the rocking of the rocker to rotate the pinion. It is operated by a pair of conical gears to operate a vehicle the screw to rotate and push the lifting sleeve to ensure that the weight rises or decline.
Instructions:
1. Before use, 
it's important to check whether the jack is normal, whether the components are flexible, add lubricating oil, and properly estimate the weight of the large object. Use a jack of appropriate tonnage and avoid overloading.
2. Adjust the technique of supporting the 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 into the rocker hole, move the deal with up and down, and the pounds will rise. When the crimson warning line appears on the lifting sleeve, the handle ought to be stopped immediately. If you want to lower the teeth in the contrary direction, the excess weight will start to fall.
Precautions:
1. Always keep the surface of the machine clean, examine the internal structure frequently, make the pinion in the rocker flexible and dependable, and lift the lifting sleeve openly.
2. The friction surface between your lifting sleeve and the housing must be oiled at any time. Other oil filling holes ought to be lubricated regularly.
3. To be able to consider the basic safety in use, avoid overloading, work with illness, it isn't appropriate to make use of multiple units to avoid danger.