Racks and spur gears are some of the important elements used in machinery. There are few mechanical devices that do not need to transmit power and motion between rotating shafts or convert rotational motion into linear motion.
Racks and gears do so with uniform motion and reliability. In addition, they span the entire range of applications from small to large.
The common situation is a spur gear meshing with another spur gear of a corresponding module, although a gear can mesh with any device having compatible teeth, such as moving linear racks.
A gear’s important feature is that gears of unequal diameters can be combined to produce a mechanical advantage, so that the rotational speed and torque of the second gear are different from that of the first.
Metric gearing uses the quantity module (m) in place of the American inch unit, Diametral Pitch (DP). The module is the length of pitch diameter per tooth and represents the size of involute gear tooth.
The unit of module is mm. Module is converted to circular pitch p by the mathematical factor pi. Pitch = pi x module. (example: module 2 has a pitch of 6.283mm).
Racks are available in all modules in a square or round profile and in standard lengths of up to 3000mm but can be supplied as continuous mount that can be joined together to achieve unlimited lengths. The spur gears have a tooth range starting at 12 teeth and depending on the module and material selected can be supplied as standard up to 140 teeth.
Racks and gears are manufactured in many materials but the most common are steel, stainless steel or plastic. Steels are commonly used because of their strength to weight ratio and low cost.
Plastic is commonly used where weight, corrosion resistance and quietness of operation is required, they can also run without the need for lubrication making them suitable for food and pharmaceutical industries. Racks & spur gears are available from T.E.A. Transmissions .