Machine Screw Jack lift and precisely positional kinds of loads from 250 pounds to 250 tons. Upright or inverted, these precision jacks operate at full capacity whether the load is in tension or compression. WJ and RWJ series single lead jacks are self-locking under full lifting capacity. DWJ and DRWJ double lead series jacks offer increased travel speed. Alloy steel input shafts, aluminium bronze worm gears and tapered roller or ball thrust bearings provide rugged reliability. Double input shafts are standard. Single input shafts are available with right or left hand extension or additional length. Jacks are available with one of four standard end conditions or special ends to meet your requirements. All Screw Jack designs can be fitted with protective boots. An optional anti-backlash feature compensates for thread wear, assuring minimum play between lifting screw and worm gear for smooth, precise operation. Jacks equipped with the anti-backlash feature are rated at full capacity under static conditions.