One’s 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 contact and developing into line get in touch with as engagement progresses. One of the most noticeable advantages of helical gears over spur gears is usually less noise, especially at moderate- to high-speeds. Also, with helical gears, multiple tooth are often in mesh, which means much less load on every individual tooth. This results in a smoother changeover of forces 
from one tooth to another, to ensure that 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 creates axial forces and heat, decreasing efficiency. These axial forces perform a significant part in bearing selection for helical gears. As the helical gear china 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 offer higher quickness and smoother movement, the helix angle is typically limited by 45 degrees because of the production of axial forces.