These gears also transmit rotary motion and torque
through a right angle. The teeth of a helical gear are inclined at an angle to
the axis of rotation of the gear.
The diagram below shows how the axis of rotation of two
helical gears are crossed at right angles. Helical gears are smoother running
than spur gears and are more suitable for rotation at high velocities. An
example of two crossed helical gears are shown below.