A Spur gear or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk with teeth projecting radially.
Though the teeth are not straight-sided (but usually of special form to achieve a constant drive ratio, mainly involute but less commonly cycloidal), the edge of each tooth is straight and aligned parallel to the axis of rotation.
These gears mesh together correctly only if fitted to parallel shafts.
Spur gears are simple, easily manufactured gears and are usually the first choice when exploring gear options. Transmitting power between parallel axes, the teeth project radially on the disc. The sole variance in their identity remains the rack, which is covered more in-depth in IHS Engineering360’s Rack and Pinion Selection Guide.
Spur gears are regularly used for speed reduction or increase, torque multiplication, resolution and accuracy enhancement for positioning systems. The teeth run parallel to the gear axis and can only transfer motion between parallel-axis gear sets. Spur gears mate only one tooth at a time, resulting in high stress on the mating teeth and noisy operation.