... .the system stiffness 4.movement is reversible high quality screw nut description:1.Screw nut bodies sliding friction bodies and rolling ... , 3.easy to process, low manufacturing cost, with self-locking function,4.the frictional torque, the transmission efficiency ... ~ 40%). 5.Ball screw nut institutions, although the structure is complex, high manufacturing costs, not self-locking, but its biggest ...