One’s teeth of a helical gear are set at an angle (in accordance with axis of the gear) and take the shape of a helix. This enables one’s teeth to mesh gradually, starting as point get in touch with and developing into series planetary gearbox contact as engagement progresses. Probably the most noticeable advantages of helical gears over spur gears can be much less noise, especially at moderate- to high-speeds. Also, with helical gears, multiple the teeth are usually in mesh, which means less load on each individual tooth. This results in a smoother transition of forces in one tooth to another, to ensure that vibrations, shock loads, and wear are reduced.
However the inclined angle of the teeth also causes sliding contact between the teeth, which creates axial forces and heat, decreasing effectiveness. These axial forces perform a significant function in bearing selection for helical gears. As the bearings have to endure both radial and axial forces, helical gears need thrust or roller bearings, which are usually larger (and more expensive) compared to the simple bearings used with spur gears. The axial forces vary in proportion to the magnitude of the tangent of the helix angle. Although bigger helix angles offer higher velocity and smoother movement, the helix angle is typically limited by 45 degrees due to the production of axial forces.