The gear has straight teeth and is parallel to the axis of the wheel. Cylindrical gear is a common type of gear. The advantages of spur gears are simple design, economical manufacture and maintenance, and no end thrust. They exert radial loads on the bearings. Gears are called slow gears. If noise is not a serious design problem, gears can be used at speed.

These gears are usually referred to as high-speed gears. Compared with spur gears of similar size, the load of helical gears. The movement of helical gear is more stable and quiet than that of spur gear. Single helical gears exert radial and thrust loads on their bearings, so thrust bearings are required. The helix angle on the gear and the gear need to be the same in size but opposite in direction, that is, the right hand pinion is meshed with the left hand gear. The intersecting but coplanar shafts connected by gears are called bevel gears. This arrangement is called a helical gear drive. Straight bevel gears can be used on shafts at any angle, but right angles are common. The bevel gear has a conical blank. The tooth thickness and tooth height of straight bevel gear are conical. A rack is a rack or bar, which can be regarded as a sector gear with a radius of curvature. By meshing the rack and pinion, torque can be converted into a linear force: the pinion rotates; the rack moves in a straight line. This mechanism is used in automobiles to convert the rotation of the steering wheel into the left and right movement of the pull rod. The rack also has the theory of gear geometry, where, for example, it can be the profile of a gear set of interchangeable racks, from which the profile of a gear with a specific actual radius can be derived. Rack and pinion type is used for rack rail.