Helical bevel gears is a type of bevel gears having helicoids teeth. It is cylindrical in shape and teeth in helix form.  The gear teeth are mounted on perpendicular shafts at an angle of 90 degree if the teeth of the gear are designed correctly. Two mating helical gears must have equal helix angle but opposite hand. The teeth are not parallel to the axis of rotation. They make less vibration and noise.  

Helical bevel gears have teeth that are cut at an angle to the face of the gear. When two teeth are engage with each other, at one end of the tooth the contact start and as the gear rotates it gradually spread until the teeths are engage with one another. This engagement makes the gears to perform their function quietly and smoothly. Due to the angle of the teeth on helical bevel gears, they create a thrust load on the gear when they mesh. Devices that use helical gears have bearings that can support this thrust load.

Helical bevel gears have two major circles: the outside circle and the pitch circle. The outside circle is the distance around the outer edge of the gear’s teeth. The pitch circle is the imaginary circle found at the point where the teeth of two gears mesh.

They are manufactured in both right-handed and left-handed configuration with a helix angle that transmits power and motion between non intersecting shafts that are parallel. An axial force is generated by inclination of teeth.  

Helical bevel gears is very expensive and require high maintenance service charge. It provides high efficiency at lower reduction rate. It saves cost and energy. Helical gears are made up of alloyed case hardening steel which is extremely strong and homogeneous structure.

Helical bevel gears is used in the transmission of aircrafts. Portable Power Tools, Lawn Movers, Textile machinery, Packaging machinery, Starter Motor, Printing Machinery, Gear Boxes, Bakery Equipment, Agriculture Machinery, Machine Tools and many more applications.