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 the teeth to mesh gradually, starting as point get in touch with and developing into series get in touch with as engagement progresses. One of the most noticeable benefits of helical gears over spur gears is usually much less noise, especially at medium- to high-speeds. Also, with helical gears, multiple tooth are at all times in mesh, which means less load 
on every individual tooth. This outcomes in a smoother changeover of forces in one tooth to another, to ensure that vibrations, shock loads, and wear are reduced.
However the inclined angle of the teeth also causes sliding get in touch with between the teeth, which helical gear china generates axial forces and heat, decreasing efficiency. These axial forces perform a significant function in bearing selection for helical gears. As 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 compared to the magnitude of the tangent of the helix angle. Although larger helix angles offer higher acceleration and smoother movement, the helix angle is typically limited by 45 degrees because of the creation of axial forces.