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 ideal for an array of applications.

One’s teeth of a spur gear planetary gearbox possess an involute profile and mesh one tooth at a time. The involute type implies that spur gears only create radial forces (no axial forces), but the approach to tooth meshing causes high stress on the gear the teeth and high noise production. Due to this, spur gears are typically used for lower rate applications, although they can be used at almost any speed.