Things to know about screws

A screw that works as connecting element is a cylindrical or conical pointed bolt or brad with a thread and that additionally has a head in varying geometrically forms at the top end. The thread can be seen as wedge or as an inclined plane that is winded spirally by rotation to get the optimal effect.

Composition and application

Screws are removable connections of all sorts of building parts. A special characteristic of screws is that they connect two or more things in a way that only the screw itself is stressed by draft and that the connected parts are fixated by adhesion. The power needed to connect the parts is called assembly prestressing force. Screws are also used as bearing type connections or stressed by bending.

Screws are implemented by screwing them in a nut thread or internal thread. While doing so, the effective length is diminished until the parts that have to be connected are pressed together. Often the nut thread is given as an additional screw or a thread is incised into the connecting component. Some screw like sheet metal screws cut the thread themself while they are turned into the material.

The head with special form serves, on the one hand, as contact point for the appropriate turning tool (screw-wrench, screwdriver, Allen wrench etc.) and, on the other hand, as thrust face to press the top part on the to be connected subjacent part.

Generally, screws are made from metal and can be produced in various sizes, forms, material and surfaces. In times of e-waste regulation and the guideline for recycling of scrap cars the screw connection is more up to date than ever.

Screws differ in the direction needed to screw them in. In mechanics, a right-handed screw thread refers to a screw that turns clockwise off the observer while it is screwed in. The referred to direction is the lengthways movement of the screw when it is screwed in. Therefore, the direction of rotation applies for screwing in (right-handed, move forward) and for screwing out (left-turning, move backwards). The screwing in of left-turning screw threads is carried out counter clockwise.


Normally, screws with heads are produced using the cold pressure procedure, which can be carried out with several stages of production. The basic material is delivered as "wire" on bobbins and is uncoiled, straightened, and, in necessary, the diameter is reduced in special machines before reaching the presses. Modern cold extrusion presses work in several steps, i.e. per stroke multiple operations are chained up after each other. During the subsequent process threat rolling machines with threat rolling dies or roller burnishing and roller burnished tools chiplessly put the threats on the screws. Depending on the diameter and length of the screws these machines can produce more than 300 pieces per minute.