Beginning with the angle of the front face, we shall find that it varies at every point in the diameter of the drill, being greatest at the outer corner and least at the centre of the drill, whatever degree of Spirality the groove or flute may possess.
"Modern Machine-Shop Practice, Volumes I and II"
Joshua Rose
The pitch of a propeller is its degree of Spirality, and is represented by the distance it would move forward if the water was a solid.
"Modern Machine-Shop Practice, Volumes I and II"
Joshua Rose