Spur gears, also known as straight-cut gears, are a common type of gear used in a wide range of applications. They are designed to transmit large amounts of power by placing them on parallel shafts which rotate in opposite directions.Spur gears consist of a cylinder with teeth around the outer edge. They have a straight tooth, involute profile which project radially and are parallel to the rotation of the axis. This allows for a smoother operation between each gear and permits greater mounting distances. Spur gears can have a central hub or be hubless and are available in a variety of pitch, hub and bore diameters. The standard pressure angles in spur gears are 14.5, 20 and 25 degrees, and refer to the angle that force is transmitted between the meshing gears.Spur gears are capable of meshing with other gears, with many gears being used to create large gear reductions. When they are meshed the gear with the most teeth is referred to as the gear, whereas the one with smaller teeth is referred to as the pinion. The size of the spur gear is described as “module”.Types of spur gearsPlastic spur gears are commonly made from acetal or nylon and have many positive characteristics including being lightweight, non-rusting and quiet. They enable low cost and large production capabilities and are also able to operate without lubrication. For hygiene reasons, plastic spur gears are an excellent choice for use in industries dealing with food production and medical equipment.Metal spur gears have more strength, load-carrying capacity and heat resilience than their plastic counterpart. They are more dimensionally stable compared to plastic and can be made from many metals such as aluminium, brass and stainless steel.What are the advantages of a spur gear?High transmission efficiencyCompact and very easy to installConstant velocity ratioNo slippage unlike belt drivesHighly reliableCan transmit large amounts of powerWhere are spur gears used?Metal cutting machinesMarine enginesMechanical clocks and watchesFuel pumpsWashing machinesGear motors and gear pumpsRack and pinion mechanismsMaterial handling equipmentAutomobile gear boxesSteel and rolling mills