A pin is a removable mechanical fastening element, of cylindrical or conical shape "Cone (geometry)"), whose ends may vary depending on the application. It is used to fix several pieces through a common hole, preventing relative movement between them. The use of these fixing systems is widely used in industrial machines and commercial products; such as closing devices, positioning of elements, pivots, etc.

Among other materials, they are mainly made of steel, since their high resistance and the wide variety of steels available allow them to be used in very different conditions of stress, corrosion, etc. Those made of brass are widely used due to their low manufacturing cost, and those made of wood are widely used in applications in which the pieces to be joined are made of wood, for example in furniture. They are designed to withstand shear stresses, hardening them to resist as much as possible, yet they are designed to break before the assembly parts are damaged.

In addition to their low cost, they have the advantage of being an easily removable mechanical connection, however sometimes it is necessary to carry out various hole preparation processes to obtain an adequate insertion. There are a wide variety of standard pin types and sizes available, as well as special designs for certain applications.

The general classification of pins is:.

Machine pins:.

Radial Fixing Pins:.

Quick release pins: