The teeth of a helical gear are set at an angle (in accordance with axis of the gear) and take the form of a helix. This allows the teeth to mesh steadily, starting as point get in touch with and developing into range get in touch with as engagement progresses. Probably the most noticeable advantages of helical gears over spur gears is usually much less noise, especially at medium- to high-speeds. Also, with helical gears, multiple teeth are usually in mesh, which means much less load on every individual tooth. This results in a smoother transition of forces from one tooth to another, to ensure that helical gear china vibrations, shock loads, and wear are reduced.
But the inclined angle of the teeth also causes sliding get in touch with between the teeth, which generates axial forces and heat, decreasing effectiveness. These axial forces play a significant function in bearing selection for helical gears. As the bearings have to endure both radial and axial forces, helical gears need thrust or roller bearings, which are typically larger (and more costly) 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 bigger helix angles offer higher quickness and smoother movement, the helix angle is typically limited by 45 degrees due to the creation of axial forces.