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 allows one’s teeth to mesh steadily, starting as point contact and developing into series contact as engagement progresses. One of the most noticeable benefits of helical gears over spur gears is usually much less noise, especially at moderate- to helical gear china high-speeds. Also, with helical gears, multiple the teeth are often in 
mesh, this means much less load on each individual tooth. This results in a smoother transition of forces from 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 play a significant part in bearing selection for helical gears. As the bearings have to endure both radial and axial forces, helical gears require thrust or roller bearings, which are usually larger (and more costly) 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 larger helix angles offer higher speed and smoother movement, the helix position is typically limited to 45 degrees because of the production of axial forces.