The teeth of a helical gear are set at an angle (in accordance with axis of the apparatus) and take the shape of a helix. This allows the teeth to mesh steadily, starting as point contact and developing into series get in touch with as engagement progresses. Probably 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 tooth are usually in mesh, which means less load on each individual tooth. This results in a smoother changeover of helical gear china forces from one tooth to the next, to ensure that vibrations, shock loads, and wear are reduced.
But the inclined angle of the teeth also causes sliding contact between the teeth, which produces axial forces and heat, decreasing efficiency. These axial forces perform a significant role in bearing selection for helical gears. As the bearings have to endure both radial and axial forces, helical gears require thrust or roller bearings, which are typically larger (and more expensive) than 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 provide higher velocity and smoother movement, the helix position is typically limited by 45 degrees because of the creation of axial forces.