Introduction to the screw cap

Bolts and screw caps are mechanical parts that are connected by a helix between them. People who have studied mechanical principles generally know . Through the spiral, the helical motion of the nut becomes a linear motion along the axis of the bolt. The fastening and removal of the coupling is achieved by tightening and loosening the screw.

If we show their spirals, the fit between them is actually equivalent to the fit of the object to the slope. The reason why objects are placed on the inclined surface is not related to their material (that is, friction) and the angle of the slope. There is a friction angle between the object and the inclined surface. As long as the angle of the inclined surface is smaller than the friction angle between the object and the inclined surface, the object will not slide off the inclined surface. This is how the nut does not loosen automatically after the nut is tightened. It is the spiral similar to the bevel, so it is very labor-saving. A small force in the spiral direction can get a large force in the axial direction of the bolt, that is, the workpiece can be tightly coupled.