sprocket

A sprocket is a wheel with teeth that mesh with a chain, belt, or track to transmit rotary motion between two shafts. Sprockets are commonly used with chains to convert and control speed and torque in bicycles, motorcycles, and industrial machinery. Unlike a gear, a sprocket relies on a chain or belt to transfer force, allowing larger center distances and stepped gear ratios.

Sprocket design centers on the chain pitch and tooth profile. The pitch is the distance between corresponding points on adjacent teeth and must match the chain being used. Sprockets are available in a range of sizes, with configurations such as single- and multiple-row teeth, solid rims, or split designs for easier maintenance. Materials vary by application, with steel providing high strength, aluminum offering light weight, and polymers used where quiet operation is desired. Sprockets are typically bored to fit a shaft, often with a keyway or set screw, and may be designed as one-piece or split-ring types for installation.

Applications include bicycle drive trains (where sprockets and cassettes determine gear ratios), motorcycles, and a variety of industrial drives such as conveyors, printing presses, and packaging lines. In engine timing systems, timing sprockets drive chains that synchronize valve and crankshaft movements; precise tooth geometry is critical in these roles to prevent jump or slip.

Maintenance involves inspecting for worn teeth, elongation, and chain wear, ensuring proper alignment and lubrication where applicable. Worn sprockets or chains should be replaced promptly, as uneven wear can accelerate damage to the entire drive system.