Both screw jacks and scissor jacks belong to mechanical jacks because their operation relies entirely on the internal structure of the machinery, and the maintenance enthusiasm of mechanical jacks should be much higher than that of hydraulic jacks. The reason is simple, which is closely related to their screw transmission.

Especially for screw jacks, scissor jacks are the most typical because scissor jacks face two situations: ① they require screw transmission to increase torque, so it is necessary to ensure smooth screw threads. ② Scissor jacks do not have an internal or external distinction, and the screw is in direct contact with the outside world, making it susceptible to external environmental influences.

Hydraulic jacks belong to a closed structure because they rely on hydraulic principles for lifting, and hydraulic oil is already present inside. Most of the grease itself has the effect of isolating air and lubricating, so the maintenance frequency of hydraulic jacks is much lower than that of mechanical jacks.