The teeth of a helical gear are set at an angle (in accordance with 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 range contact as engagement progresses. One of the most noticeable benefits of helical gears over spur gears is usually less noise, especially at moderate- to high-speeds. Also, with helical gears, multiple teeth are always in mesh, which means less load on each individual tooth. This outcomes in a smoother transition of forces in one tooth to another, so that vibrations, shock loads, and wear are reduced.
But the inclined angle of the teeth also gear rack causes sliding get in touch with between your teeth, which creates axial forces and heat, decreasing performance. These axial forces enjoy a significant part 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 compared to the magnitude of the tangent of the helix angle. Although bigger helix angles provide higher rate and smoother motion, the helix angle is typically limited by 45 degrees because of the production of axial forces.