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 allows the teeth to mesh gradually, starting as point get in touch with and developing into range get in touch with as engagement progresses. One of the most noticeable advantages of helical gears over spur gears can be much less noise, especially at medium- to high-speeds. Also, with helical gears, multiple teeth are at all times in mesh, which means much less load on every individual tooth. This planetary gearbox results in a smoother changeover 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 your teeth, which produces axial forces and heat, decreasing effectiveness. These axial forces perform a significant role 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 in proportion to the magnitude of the tangent of the helix angle. Although bigger helix angles provide higher quickness and smoother motion, the helix angle is typically limited to 45 degrees due to the production of axial forces.