Roll Pin Specifications

Roll pins are predominately used in mechanical engineering and metalwork.is sharp of metal image by Victor M. from Fotolia.com

A roll pin, also known as a spring or sellock pin, is a metal fastener used in mechanical engineering and metalwork. A narrow steel or alloy rod, the pin is normally hammered into a hole that will join two metal objects. Its shape gives the pin its ability to withstand pressure and rotational friction. Because roll pins are used in various forms of machinery, they come in many lengths, widths and thicknesses depending on their intended purpose.

Dimensions

Roll pins are flat pieces of steel that are rolled to form a "C" shape. The hollow opening allows for flexibility under pressure; it contracts to fit what it will help secure. Lengths of roll pins vary from 4 to 120 inches, but they can be custom-ordered in larger sizes. The diameters for spring pins range from 0.8 to 20 inches.

Heavy-duty pins are thicker and stronger than standard or light-duty pins. The durability of the pin, and thus its ability to perform, depends on the balance between strength and flexibility. A pin that is not strong enough could result in it bending or contorting under pressure. On the other hand, if a roll pin is too strong or rigid for the hole, it might not be yielding enough, resulting in damage to the hole.

Steel is the metal that most manufacturers use for making roll pins, although the type of steel can vary. One popular material is high-carbon steel, which is an alloy steel with 0.99-percent carbon content, making it very durable. Other durable alloy materials, such as chromium and vanadium, are also used as a substitute for carbon. Stainless steel is another widely used material for roll pins, as chrome or nickel-plated varieties are known for their strength.

Lubrication and finishes help with roll pin installation and keep them from stripping in high-friction areas. Standard pins are normally oiled, but there are other finishes available, such as passivated oil, which coats stainless steel with a protective oxide layer. Other coatings include phosphate, which is used to protect steel from corrosion. It is a sprayed coating method that uses magnesium, iron or zinc. Some suppliers offer a zinc-plated roll pin, which can help substantiate an alloy pin.