Machinery Repairman

c. This angle is obtained by subtracting the
dedendum angle ( ) from the pitch
cone angle (
4. Addendum angle
a. This angle is formed by the top of the tooth
and a line one addendum down on the
tooth.
b. This angle cannot be measured, but it is
used in making calculations for the gear.
c. In the triangle shown in figure 14-16, view
A, the hypotenuse is the pitch cone radius
and the side opposite is the addendum.
Therefore, Cot
Figure 14-16.—Development of bevel gear formulas.
14-17
5. Dedendum angle ( ) (fig. 14-15)
a. This angle is formed by a line
addendum down on the tooth and a
drawn through the bottom tooth.
b. This angle cannot be measured, but
used in calculations.
c. In the triangle shown in figure 14-16, view
B, the side opposite the dedendum angle is
the dedendum and the hypotenuse is the
pitch cone radius.
Therefore, Cot
6. Back cone angle (BCA or (fig. 14-15).
This angle is formed by the large end of the
tooth and the pitch diameter of the gear. It is
equal in value to the pitch cone angle (PCA).