What are pin fasteners?
Pin fasteners are primarily used to secure or join parts where the primary force acting on the parts is shear, an opposing force that pushes one part of the pin in one direction and the other part in the opposite direction promote.
Pins are not well suited for applications where they are primarily subject to axial forces that pull or push the pin or connecting component in a direction parallel to the axis of the pin. Pins held by a securing mechanism, such as cotter pins or hitch pin clamps, can be used where some axial forces are generated due to rotation or vibration. However, threaded fasteners such as bolts are more suitable for applications with larger axial forces.
Because pins are used in non-threaded holes, friction or tension is usually required to hold them in place. One of the main differences between fastening pin designs is how they are secured.
Slip fit: Since the diameter of the hole is larger than the diameter of the pin, there is little friction between the pin and the hole. The pin may fall out of or pass through the hole, so do not use a slip fit in through-hole applications unless the pin is otherwise retained.
Press fit: The diameter of the pin is slightly larger than the hole. When the pin is installed, the pin or hole deforms slightly, causing the two parts to exert a radial force that holds the pin in place. The press fit creates significant holding force against axial movement of the pin, although the axial holding force is less than that of a comparably sized bolt. Press-fit fasteners are also called interference fits or friction fits.
Spring Force: Pins designed to compress, exert a spring force against the sides of the hole; examples include slotted spring pins and helical spring pins.
Clips and pins: Insert the retaining clips and pins into the holes of the larger pins so they cannot come out. Examples include bridge pins, safety pins, and cotter pins.
Pawl: A pawl is a mechanism with a ball or latch that protrudes from the surface of the pin. The brake rests on a spring so it can be compressed during installation and removal. Pawls are available in detent pins and unsplit clevis pins.
How are pin fasteners made?
Metal fastener pins are formed from metal rods, wires or sheets. Depending on the type of pins they go through different processes. Manufacturing processes include:
Cutting: Cutting rod or wire into desired size.
Wire forming: The wire is formed on a wire forming machine and undergoes processes such as bending, stamping and upsetting. Learn more about wire forming and wire forming machines.
Turning: Larger diameter pins are turned on a lathe. Lathes spin parts at high speed and remove material with cutting tools. Turning is used to shape, groove, drill and machine parts for pins.
Grinding: Pins can be ground to add features like chamfers or to achieve precise specifications with tight tolerances. This process is critical for the pins that will be pressed into place, where the exact diameter is critical.
Drilling: Pins can be drilled to make holes for other fasteners, clips or detents.
Rolling: Spring pins are manufactured by rolling metal strip into tubes or coils.
Heat Treatment: Steel pins can be hardened through heating and cooling processes that change their metallurgical properties.
Finishing: Finishing adds a coating to the surface of the pin. Fastener pins are available in a variety of surface treatments, including chromate conversion coating, phosphate coating, electroplating and passivation. They are also available as regular unfinished parts
