One’s teeth of a helical gear are set at an angle (in accordance with axis of the gear) and take the form of a helix. This allows the teeth to mesh steadily, starting as point get in touch with and developing into series contact as engagement progresses. One of the most noticeable benefits of helical gears over spur gears is less noise, especially at moderate- to high-speeds. Also, with helical gears, multiple teeth are constantly in mesh, which means much less load on every individual tooth. This results in a smoother changeover 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 get in touch with between the teeth, which creates axial forces and heat, decreasing performance. 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 need thrust or roller bearings, which are usually larger (and more expensive) 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 bigger helix angles offer higher swiftness and smoother movement, the helix angle is typically helical gear china limited to 45 degrees because of the production of axial forces.
