One’s teeth of a helical gear are set at an angle (relative to axis of the apparatus) and take the shape of a helix. This enables one’s teeth to mesh gradually, starting as point contact and developing into line contact as engagement progresses. One of the most noticeable benefits of helical gears over spur gears is certainly less noise, especially at moderate- to high-speeds. Also, with helical gears, multiple the teeth are generally in mesh, this means less load on each individual tooth. This helical gear china outcomes in a smoother changeover of forces in one tooth to the next, so that vibrations, shock loads, and wear are reduced.
However the inclined angle of one’s teeth also causes sliding contact between your teeth, which produces axial forces and heat, decreasing performance. These axial forces enjoy 
a significant role in bearing selection for helical gears. Because the bearings have to endure both radial and axial forces, helical gears require thrust or roller bearings, which are usually larger (and more expensive) than the simple bearings used with spur gears. The axial forces vary compared to the magnitude of the tangent of the helix angle. Although larger helix angles provide higher rate and smoother motion, the helix position is typically limited to 45 degrees because of the production of axial forces.