One’s teeth of a helical gear are set at an angle (relative to axis of the gear) and take the shape of a helix. This allows one’s teeth to mesh steadily, starting as point get in touch with and developing into line contact as helical gear china engagement progresses. One of the most noticeable benefits of helical gears over spur gears is usually much less noise, especially at moderate- to high-speeds. Also, with helical gears, multiple teeth are generally in mesh, this means much less load on each individual tooth. This results in a smoother transition of forces from one tooth to another, to ensure that vibrations, shock loads, and wear are reduced.

However the inclined angle of one’s teeth also causes sliding contact between the teeth, which generates axial forces and heat, decreasing efficiency. These axial forces play a significant part in bearing selection for helical gears. Because the bearings have to withstand both radial and axial forces, helical gears require thrust or roller bearings, which are usually larger (and more costly) than the simple bearings used in combination with spur gears. The axial forces vary compared to the magnitude of the tangent of the helix angle. Although larger helix angles offer higher velocity and smoother movement, the helix angle is typically limited by 45 degrees due to the production of axial forces.