b. Pitch Diameter (PD)
g. Whole Depth (WD)2.15708
(1) Diameter of the pitch circle.
(1) The sum of an addendum and a
(2) For every tooth in the gear there is an
addendum on the pitch diameter.
(2) 1.0000 - ADD
(3) ADD × NT = PD
+1.1570 - DED
c. Outside Diameter (OD).
2.1570 - WD
(1) The diameter of the gear.
h. Diametral Pitch (DP)
(2) Since there is an addendum on the pitch
(1) The ratio of the number of teeth per inch
diameter for each tooth, the two elements are directly
of pitch diameter.
related. Therefore, the outside diameter is simply the
pitch diameter plus two addendums, or simulated teeth.
The formulas read:
i. Chordal Addendumac
(a) ADD × NT = PD
(1) The distance from the top of a gear tooth
(b) ADD × (NT) + 2) = OD
to a chord subtending (extending under) the
(c) PD + 2ADD = OD
intersections of the tooth thickness arc and the sides of
d. Linear Pitch (LP)
(1) The linear pitch is the same as the
circular pitch except that it is the lineal measurement of
pitch on a gear rack
j. Chordal Thicknesstc
(2) CP = LP
(1) The thickness of the tooth, measured at
(3) Figure AIV-2 illustrates linear pitch.
the pitch circle.
3. GEAR AND TOOTH ELEMENT RELATION-
2. GEAR ELEMENTS
a. Number of Teeth (NT)
(1) Connecting link between the tooth
elements and gear elements.
(2) Number of teeth in the gear
Figure AIV-2.Linear pitch.