In the case of machining helical gears, the tool moves along the rotation axis of the gear blank, which is the same as the tool path in spur gear machining. The cutter and blank motion of helical gear machining are shown in the figure.
The cutter moves in a straight line along the rotation axis of the gear blank, and the gear blank and the helix angle β Synchronous rotation. When the tool moves La, the gear blank must move the length FA on the pitch surface because the tooth groove is at a helical angle β Tilt to the rotation axis. Therefore, the gear blank rotates θ a 。 These relationships are shown in the formula.
