Spur gears are a type of planetary gearbox cylindrical equipment, with shafts that are parallel and coplanar, and teeth that are straight and oriented parallel to the shafts. They’re arguably the simplest and most common type of gear – simple to manufacture and ideal for an array of applications.
One’s teeth of a spur gear have got an involute profile and mesh one tooth at a time. The involute type means 
that spur gears just produce radial forces (no axial forces), but the method of tooth meshing causes high stress on the gear the teeth and high noise production. Because of this, spur gears are usually used for lower rate applications, although they can be utilized at nearly every speed.