30 Ton Machine Screw Jack WJ1130, WJ3230, DWJ1130, DWJ3230 Joyce 30-ton worm gear machine screw jacks lift and precisely position loads. Upright or inverted, these jacks operate at full capacity in tension or compression and are available in Translating, Keyed for non-rotation and KFTN designs. WJ, single lead jacks are self-locking.