Cogwheel

A cogwheel is a wheel with regularly spaced teeth that mesh with another toothed wheel to transmit mechanical power and motion. When two cogwheels mesh, rotation of one causes rotation of the other, with a gear ratio determined by the number of teeth. Cogwheels are a subset of gears, typically used for transmitting motion between shafts that run parallel.

The most common cogwheels have straight teeth and are called spur gears; other forms such as helical and bevel gears use angled teeth to reduce noise or to operate on non-parallel shafts. Modern cogwheels are designed using standard teeth profiles, most commonly the involute profile, which provides constant contact ratio as the wheels rotate. Key parameters include the module (or diametral pitch), the number of teeth, pitch diameter, and backlash.

Cogwheels are manufactured from steel, cast iron, bronze, or aluminum, with heat treatment and surface finishing to withstand wear. Common processes include hobbing, shaping, and milling. Lubrication and proper alignment are important for efficiency and longevity.

In applications, cogwheels form gear trains used in clocks, automotive transmissions, industrial machinery, and machinery drives. Limitations include noise at high speeds, wear under heavy loads, and the need for precise machining to maintain mesh. Modern systems often pair cogwheels with other gear types to optimize performance.