Jack Screws
A jack screw is a mechanism that uses a long threaded rod to position a matching nut at any position along its length. In a jack screw, forces acting on the nut along the length of the rod do not appreciably affect the rotation of the rod. In general, jack screws are not considered self-locking. Jack screws are designed for both tensile and compressive loads and can work in any orientation or mounting position.
There are many variations among jack screws. They are available in a wide range of speeds, load capabilities, end fittings, and mounting arrangements. They can also be synchronized with other jack screws. Jack screws commonly use an acme along the threaded rod, which gives the screw strength and resistance to the large loads imposed on most jack screws. At the same time, the screw is not severely weakened by wear over many rotations. In order to lubricate a jack screw, grease is most typically used.
Jack screws are widely used in many common applications. With the ability to push, pull, lift, lower and position loads of many sizes, they serve many useful purposes. They can operate in very harsh conditions, including nuclear applications. Other typical uses include car-locks, railway applications, securing connectors in computer and other electronic equipment, linear actuators, and many more.