The teeth of a helical gear are set at an angle (relative to axis of the gear) and take the form of a helix. This enables one’s teeth to mesh steadily, starting 
as point contact and developing into line get in touch with as engagement progresses. One of the most noticeable benefits of helical gears over spur gears is definitely less noise, especially at medium- to high-speeds. Also, with helical gears, multiple tooth are at all times in mesh, this means less load on every 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.
But the inclined angle of one’s teeth also causes sliding contact between the teeth, which produces axial forces and heat, decreasing effectiveness. 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) than the simple bearings used with spur gears. The axial forces vary compared to the planetary gearbox magnitude of the tangent of the helix angle. Although bigger helix angles offer higher velocity and smoother motion, the helix position is typically limited by 45 degrees due to the creation of axial forces.