What is a defining feature of helical gears compared to spur gears?

Helical gears are characterized by their teeth being angled in a helical shape, which allows for smoother engagement as the teeth gradually come into contact. This gradual engagement reduces noise and vibration during operation, making helical gears typically quieter than spur gears, which have teeth that are parallel to the gear axis and engage suddenly.

This design contributes to a more continuous and smooth transfer of power, resulting in less vibration and reduced operational noise. In contrast, spur gears tend to produce more abrupt sound due to the way their teeth mesh together.

The other features of helical and spur gears differentiate them in other ways, such as load capacity, manufacturing cost, and backlash; however, the reduced noise during operation is the most prominent and defining feature of helical gears compared to their spur counterparts.