The 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 the teeth to mesh gradually, starting as point contact and developing into series get in touch with as engagement progresses. Probably the most noticeable benefits of helical gears over spur gears can be much less noise, especially at moderate- to high-speeds. Also, with helical gears, multiple the teeth are often in mesh, this means less load on each individual tooth. This outcomes in a smoother transition of forces from one tooth to another, so 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 role in bearing selection for helical gears. As the bearings have to withstand both radial and axial forces, helical gears need thrust or roller bearings, which are typically 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 bigger helix angles provide higher speed and smoother motion, the helix position is typically limited by 45 degrees due to the production of axial forces.