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 allows the teeth to mesh gradually, starting as point contact and developing into collection get in touch with as engagement progresses. One of 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 constantly in mesh, which means less load on each individual tooth. This results in a smoother changeover of forces in one tooth to another, so that vibrations, shock loads, and wear are reduced.
But the inclined angle of one’s teeth also causes sliding get in touch with between your teeth, which produces axial forces and heat, decreasing effectiveness. These axial forces play 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 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 offer higher quickness and smoother motion, the helix position is typically limited by 45 degrees because of the helical gear china production of axial forces.