screw jack lift; Safely self locking, Positioning Precision, Heavy Duty, Uniform Lifting Speed, Low Efficiency, Use Infrequentl screw jack lift ... , Worm Shaft, Taper Roll Bearings, Seals, Housing, Self-locking Trapezoidal Screw,etc.* Model: RN-0.5ton, RN-1 ton ... Manual Operation and Electrical Operation are available.* Multiple Screw Jack Systems are availbale and fully synchronized.* Absolutely ...