A plow bolt is a type of fastener that is used for making mechanical connections that require a smooth, or flush, surface at the location where the bolt head protrudes. These were so named because of their early use in the manufacture of plows. Today plow bolts are used on many types of heavy construction equipment, such as snowplows, road graders, and scoop shovels. Plow bolts are normally exposed to high forces and wear, and it is important to select the right bolt for each individual application.
A plow bolt is used in combination with a nut. It has a large head on one end and a cylindrical shaft with an external thread, which is a helical rib that allows the nut to be advanced when rotated. The head of a plow bolt is countersunk with a short, square neck to prevent the bolt from turning when the nut is tightened or removed. The nut, which is usually hexagonal in shape, has a hole with an internal thread that matches the thread of the plow bolt.
Plow bolts are tightened or loosened by applying torque to the nut. When the nut is rotated clockwise, it will advance along the thread of the bolt and tighten the mating objects together. A high amount of clamping force can be generated when the bolt and nut are tightened against two or more objects located between them. The mating surfaces between the bolt and nut resist the force being applied, and help to prevent the mechanical connection from loosening over time.
The head of a plow bolt is usually flat, or has a slight dome shape to ensure a smooth surface is maintained at the location of the bolt. The low profile of the head is a primary feature of the plow bolt. Because the bolt head is flush with the mating surface, the head is often exposed to high wear. For example, snowplow blades must have a flat surface against the ground being plowed to ensure the snow is removed effectively. Plow bolts used in the manufacture of snowplow blades will be exposed to the same forces as the blade as it is dragged across the ground.
Plow bolts come in a variety of standard and metric sizes. The type and size of the plow bolt selected for a particular application depends upon the forces and environment that the mechanical connections will be exposed to. They are manufactured using carbon steel, stainless steel, and metal alloys for high wear resistance. The material used is often heat-treated or hardened to provide improved wear resistance and extend the useable life of the bolt.