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A screw jack consists of a heavy-duty vertical screw with a load table mounted on its top, which screws into a threaded hole in a stationary support frame with a wide base resting on the ground. A rotating collar on the head of the screw has holes into which the handle, a metal bar, fits.
The square thread form is a common screw thread profile, used in high load applications such as leadscrews and jackscrews. It gets its name from the square cross-section of the thread. [ 1 ] It is the lowest friction and most efficient thread form, but it is difficult to fabricate.
A leadscrew (or lead screw), also known as a power screw [1] or translation screw, [2] is a screw used as a linkage in a machine, to translate turning motion into linear motion. Because of the large area of sliding contact between their male and female members, screw threads have larger frictional energy losses compared to other linkages.
A scissor jack uses the mechanical advantage of a leadscrew and 4-bar linkage to allow a human to lift a vehicle by manual force alone. They are inexpensive and are common in manufacturer-supplied breakdown kits. The jack shown at the left is made for a modern vehicle and the notch fits into a jack-up point [3] on a unibody. Earlier versions ...
The screw thread concept seems to have occurred first to Archimedes, who briefly wrote on spirals as well as designed several simple devices applying the screw principle. Leonardo da Vinci understood the screw principle, and left drawings showing how threads could be cut by machine. In the 1500s, screws appeared in German watches, and were used ...
In oil field tubing, buttress thread is a pipe thread form designed to provide a tight hydraulic seal. The thread form is similar to that of Acme thread [10] but there are two distinct threaded portions of differing diameters and profiles, the larger having a wedging profile, with a tapered sealing portion in between the larger and smaller diameters.
Cutting a single helical groove into a screw-stock cylinder yields what is referred to as a single-thread screw. Similarly, one may construct a double-thread screw provided that the helix angle of the two cuts is the same, and that the second cut is positioned in the uncut material between the grooves of the first.
Where L e is the thread engagement length, A t is the tensile stress area, D is the major diameter of the screw, and p is the pitch. This equation only holds true if the screw and female thread materials are the same. If they are not the same, then the following equations can be used to determine the additional thread length that is required: [14]