The teeth of a helical gear are set at an angle (relative to axis of the apparatus) and take the shape of a helix. This enables one’s teeth to mesh gradually, starting as point contact and developing into series contact as engagement progresses. One of the most noticeable advantages of helical gears over spur gears is usually less noise, especially at medium- to high-speeds. Also, with helical gears, multiple teeth are at all times in mesh, this means less load on every helical gear china individual tooth. This outcomes in a smoother transition 
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 contact between the teeth, which creates axial forces and heat, decreasing efficiency. These axial forces play a significant function 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 usually larger (and more costly) compared to 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 offer higher quickness and smoother movement, the helix angle is typically limited by 45 degrees due to the production of axial forces.