Spur gears are a type of cylindrical gear, with shafts that are parallel and coplanar, and teeth that are directly and oriented parallel to the shafts. They’re arguably the simplest and most common kind of gear – simple to manufacture and suitable for an array of applications.
One’s teeth of a spur gear have an involute profile and mesh one tooth at a time. The involute form planetary gearbox implies that spur gears only produce radial forces (no axial forces), but the 
method of tooth meshing causes high pressure on the gear the teeth and high noise creation. Due to this, spur gears are usually used for lower rate applications, although they can be utilized at almost any speed.
