Helical cylindrical gear is a kind of helical gear. It is called helical cylindrical gear only when the two shafts are parallel (as shown in the figure). It has the following advantages:
(1) The number of teeth in contact during transmission is large, the transmission is uniform and the noise is small.
(2) It can transmit great power.
(3) It can be used when two axes are parallel to each other or at any angle without intersecting.
Therefore, helical gears are widely used, especially helical mesh cylindrical gears. Helical cylindrical gears are also used in modern high-speed transmission, high impact transmission and high-power transmission, such as direct transmission of motor and gear transmission of diesel engine. Helical cylindrical gears are also used in the end milling head of machine tool.