Shearpins

A shearpin, also known as a shear pin or shearbolt, is a fastener designed to break or shear when a certain load is applied. Its primary function is to protect machinery from damage by acting as a sacrificial component. When an overload condition occurs, such as a blockage in a mechanism or a sudden impact, the shearpin fails, disconnecting the driving force from the driven component. This prevents more expensive parts of the machinery, like gears, motors, or shafts, from being stressed beyond their limits and breaking.

Shearpins are typically made from materials with a known shear strength, such as mild steel or brass. The specific material and dimensions of the pin are chosen based on the expected operating loads and the desired overload protection level. They are often used in applications like agricultural equipment (e.g., PTO shafts on tractors), snow blowers, conveyors, and outboard motors.

Replacing a shearpin is generally a straightforward and inexpensive repair compared to fixing the machinery it protects. The shearpin acts as a deliberate weak point in a system, ensuring that failure occurs in a controlled and predictable manner. This concept is a form of mechanical fuse.