What Are Plow Bolts and Their Uses?

Plow bolts are a specialized type of fastener. These are similar to carriage bolts, but the head of a plow bolt is concave or flat. The underside of the head tapers down into a cone-shape which is engineered to fit into a countersunk recess. Countersunk recesses are designed to accommodate particular plow bolts. Many of the bolts have a square base, but some can have a key or a locking slot instead. They come in both metric and standard sizes. Hardened or heat-treated carbon steel and stainless steel are the most common materials used to make plow bolts.

What Are They Used For?

Plow bolts are used when the surface where the bolt head would normally stick out needs to be smooth. Originally, they were mainly used for plows–hence the name. Now there are many different applications. A lot of heavy equipment requires the use of this type of bolt. Snowplows are one such example. An effective snowplow blade runs a smooth surface against the pavement to get rid of the snow. If the heads of the bolts are not flat, then they can gouge the ground and wear much quicker.

Some of the other types of equipment that uses this bolt are road graders, tractors, scoop shovels and bulldozers. There are even plow bolt bits–pictured below–like the ones used in the Dura Disk II cutting system for grinders. They have the square base and are very strong like a plow bolt, but they have a shaped head for cutting instead of a flat one.

How to Attach or Remove a Plow Bolt

When a plow bolt is put into its countersunk recess, it is held in place by the base (usually square-shaped but there are other types of bases, as mentioned earlier in this article) and a nut. The base keeps the plow bolt from turning when removing or tightening the nut. The nut is put on the end of the shaft of the bolt. The shaft has an external thread that the nut advances up towards the head of the bolt when it is rotated. To tighten the bolt, you use a tool to rotate the nut clockwise until it meets the underside of the object(s) being held together. Do not over-tighten the nut and bolt as you could accidentally shear the end of the bolt off. This happens more often than you think when using power tools to rotate the nut, so be cautious. To remove the bolt, you turn the nut counter-clockwise until you can remove it from the end of the shaft.

Where to Buy Them

If you need to replace a plow bolt, it is best to get it either directly from the manufacturer of your equipment or a retailer recommended by them. It is very important that you purchase the right bolt. For example, if the plow bolt is for a snowplow blade you need to select one that will withstand the forces it is exposed to as the blade is dragged across the ground–and it needs to fit in the countersunk recess properly. A grade 5 bolt, which is used for equipment like road graders, probably will not make a good replacement. Most snowplow blades use grade 8 plow bolts, unless stated otherwise by the manufacturer.