From the portion b half the thickness of the tooth at the pitch line is obtained.
The pitch line is then drawn at a radius of 1.606 of the pitch from the worm axis.
The mortise spur-wheels have a diameter of 22 feet at the pitch line, with two rows of teeth, each 15 inches face.
When two gears of equal size mesh together, the pitch line, or the pitch circle, as it isp.
That part of a gear wheel tooth that extends beyond or outwards from the pitch line.