A gear is a rotating circular machine part having cut teeth or, in the case of a cogwheel or gearwheel, inserted teeth, which mesh with another (compatible) toothed part to transmit rotational power. While doing so, they can change the torque and rotational speed being transmitted and also change the rotational axis of the power being transmitted. The teeth on the two meshing gears all have the same shape.
Iron gears, Han dynasty
Wooden cogwheel driving a lantern pinion or cage gear
A cast gearwheel (above) meshing with a cogged mortise wheel (below). The wooden cogs are held in place by nails.
Helical gears Top: parallel configuration Bottom: crossed configuration
Machine element or hardware refers to an elementary component of a machine. These elements consist of three basic types:structural components such as frame members, bearings, axles, splines, fasteners, seals, and lubricants,
mechanisms that control movement in various ways such as gear trains, belt or chain drives, linkages, cam and follower systems, including brakes and clutches, and
control components such as buttons, switches, indicators, sensors, actuators and computer controllers.
NSK Support Roller cut (cropped)