Profile shift coefficient – Gear Terminology
Gear teeth are sometimes shifted to prevent undercutting or to adjust the center distance between gears. In this case, the reference pitch line of the gear cutting tool is shifted radially from the position for cutting of a standard gear.
The amount by which the gear cutting tool is displaced is the extra feed of gear cutter xm (mm), and the profile shift coefficient x is the value obtained by dividing the extra feed of gear cutter xm by the module m.
If the profile shift coefficient is positive (e.g., x = +0.5), the tooth has a positive correction, the tooth thickness increases, and the tooth is more resistant to bending. If the value is negative, the tooth will have a negative correction and the tooth thickness will decrease.
(Left) Negative shifting
(Right) Positive shifting