One’s teeth of a helical gear china helical gear are set at an angle (in accordance with axis of the apparatus) and take the form of a helix. This enables one’s teeth to mesh gradually, starting as point get in touch with and developing into range get in touch with as engagement progresses. Probably the most noticeable advantages of helical 
gears over spur gears can be less noise, especially at moderate- to high-speeds. Also, with helical gears, multiple teeth are usually in mesh, this means much less load on each individual tooth. This outcomes in a smoother changeover of forces from one tooth to the next, to ensure that vibrations, shock loads, and wear are reduced.
However the inclined angle of one’s teeth also causes sliding get in touch with between the teeth, which produces axial forces and heat, decreasing effectiveness. These axial forces play a significant part in bearing selection for helical gears. Because the bearings have to endure both radial and axial forces, helical gears need thrust or roller bearings, which are typically larger (and more costly) compared to the simple bearings used in combination with spur gears. The axial forces vary in proportion to the magnitude of the tangent of the helix angle. Although larger helix angles provide higher speed and smoother motion, the helix angle is typically limited to 45 degrees because of the creation of axial forces.