1000 lbs machine screw jacks Jacton jt-0.5t 1000 lbs miniature worm gear machine screw jacks with 1:5, 1:10, 1:20 worm gear set ratios lift and precisely position up to 1000 pounds. Upright or inverted, these jacks operate at full capacity in tension or compression. Available in Translating, Traveling nut and Keyed designs, they have self-lock, no require a brake or external locking device to hold position.