One’s teeth of a helical gear are set at an angle (relative to axis of the apparatus) and take the form of a helix. This enables the teeth to mesh gear rack steadily, starting as point contact and developing into line get in touch with as engagement progresses. Probably the most noticeable benefits of helical gears over spur gears can be less noise, especially at moderate- to high-speeds. Also, with helical gears, multiple teeth are constantly in mesh, this means less load on every individual tooth. This outcomes in a smoother changeover of forces in one tooth to the next, 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 generates axial forces and heat, decreasing performance. These axial forces enjoy a significant function 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 typically larger (and more expensive) 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 swiftness and smoother movement, the helix position is typically limited by 45 degrees because of the production of axial forces.