This gear is used for applications that require very
quiet and smooth running, at high rotational velocities.
Parallel helical gears have their teeth inclined at a
small angle to their axis of rotation. Each tooth is part of a spiral or helix.
The helical gears shown below have splines cut in their center holes. The gears
can move along a splined (grooved) shaft, although they rotate with the shaft.
An example of a helical gear is shown below.
Double helical gears give an efficient transfer of
torque and smooth motion at very high rotational velocities. An example of a
double helical gear is shown below.