Helical gears are one type of cylindrical gears with slanted tooth trace. Compared to spur gears, they have the larger contact ratio and excel in quietness and less vibration and able to transmit large force. A pair of helical gears has the same helix angle but the helix hand is opposite.
When the reference section of the gear is in the normal plane, by tilting the hobbing tool, the spur gear hobbing machine and hobbing tool can be used to produce helical gears. Because of the twist of teeth, their manufacturing has the disadvantage of more difficult production. Our company manufacture helical gears by Powder Metallurgy process.
Helical gears are used increasingly often as power transmitting gears, since not only can they carry larger loads because of their lower dynamic load but also their noise and vibration levels in operation are lower compared with those of spur gears.