What Is a Spur Sprocket on a Chain Saw?

Power Train

• A chain saw is made of of four basic components, including the engine, the sprocket, the chain and the guide bar. The engine provides the power that drives the chain saw. The sprocket receives the power from the engine and uses it to drive the chain around the guide bar.

Spur Sprocket

• Chain saw sprockets typically come in two varieties: sprocket systems and spur sprockets. Sprocket systems have two or more pieces, which may include a rim sprocket and a spline. Spur sprockets are one-piece units. Spur sprockets are available in a variety of chain pitches and number of teeth based on the type of chain saw they are intended to be used with.

Advantages

• A spur sprocket has the advantage of economy over sprocket systems. Since a spur sprocket comes in one piece, it is typically less expensive than a sprocket system. Spur sprockets are usually easier and faster to replace than sprocket systems. Consumer chain saws are more likely to use a spur sprocket than a sprocket system because consumers who can handle a chain saw are likely to be able to change a spur sprocket without professional assistance.

Replacement

• The spur sprocket is typically located behind a protective shield or plate directly behind the guide bar. You can usually get to the spur sprocket by removing the mounting bolts that hold the shield and guide bar in place. With the guide bar mounting bolts loose, you can easily remove the chain and the guide bar. The spur sprocket is usually held in place by a C fastener or cotter key. Replacement is a matter of pulling the old sprocket off and slipping a new sprocket into place. Use caution any time you work on a chain saw. The blades are extremely sharp and can cause serious injury. Always wear heavy duty work gloves any time you handle the chain.