Introduction to the basic parameters of the gear:

Addendum circle: The circle passing through the top of all teeth of the gear is called the addendum circle. Its radius is denoted by ra, and its diameter is denoted by da.

Root circle: The circle passing through the bottom edge of all tooth slots becomes the root circle. Its radius is represented by rf, and its diameter is represented by df.

Index circle: In order to facilitate the calculation of the size of each part of the gear, a circle is selected on the gear as the basis for calculation, and this circle becomes the index circle. The radius is denoted by r and the diameter is denoted by d. Various parameters on the index circle do not have an angle mark.

Addendum height: The part of the gear teeth between the index circle and the addendum circle is called the addendum, and its radial height is called the addendum height. represented by ha.

Root height: The part of the gear teeth between the index circle and the root circle is called the root, and the radial height is called the root height. Indicated by hf.

Total tooth height: The radial height of the gear tooth between the tip circle and the root circle is called the total tooth height, which is represented by h.

Tooth thickness: On any circumference, the arc length between the tooth profiles on both sides of the gear teeth is called the tooth thickness on the circumference, and is represented by sk.

Cogging width: The space between two adjacent teeth of a gear is called the cogging. On any circumference, the arc length of the cogging is called the width of the cogging on the circumference, denoted by ek.

Pitch: On any circle, the length of the arc on the same side of two adjacent teeth is called the pitch on the circle, expressed by Pk.

On the base circle, the length of the arc on the same side of two adjacent teeth is called the pitch of the base circle, represented by Pb.

Normal pitch: the distance between the two adjacent teeth on the same side in the normal direction is called the normal pitch, which is represented by Pn. According to the involute properties, Pn=Pb°