The jack housings are made of ductile iron and proportioned to support the rated capacity of the unit . models have aluminum housings . This is jack incorporates an alloy steel worm which drives a high strength bronze worm gear ( drive sleeve ) . The worm shaft is supported on anti - friction tapered roller bearings with external seals provided to prevent loss of lubrication . The drive sleeve is supported on anti-friction tapered roller or ball thrust bearings . rotation of the drive sleeve causes the lifting screw to translate or rotate , depending upon jack configuration .
The working principle of the hand operated worm gear screw jack is that the worm ( also called the input shaft ) is manually rotated by the hand wheel . the worm wheel (also called the worm gear ) is rotated by the worm , and the trapezoidal lifting screw is moved by the rotating worm wheel .
