Here is another guide to help you determine the various specifications of a gear.
How to Find “Ratio”
RULE : Divide the Number of Teeth in the Gear by the Number of Teeth in the Pinion
SOLUTION : Teeth in Gear 48
Teeth in Pinion 24
48 ÷ 24 = ratio 2:1
Ratio = 2:1
How to Find “Diametral Pitch (DP)”
RULE : Divide 3.1416 by the Circular Pitch
SOLUTION : Circular Pitch .2618"
3.1416÷.2618 = 12
Diametral Pitch (DP) 12
How to Find “Pitch Diameter of Pinion”
RULE : Divide Number of Teeth in the Pinion by the D.P.
SOLUTION : Number of Teeth in Pinion 24
D.P. (Diametral Pitch) 12
24÷ 12 = 2" Pitch Diameter
How to Find “Pitch Diameter of Gear”
RULE : Divide Number of Teeth in the Gear by the D.P
SOLUTION : Number of Teeth in Gear 48
Diametral Pitch 12
48÷12 = 4" Pitch Diameter
How to Find “Whole Depth (of Tooth)”
RULE : Divide 2.188 by the Diametral Pitch and add .002
SOLUTION : Diametral Pitch (DP) = 12
(2.188÷12) + .002 = .1843"
Whole depth of Tooth = .1843"
How to Find “Addendum for Pinion”
RULE : Having Ratio Use Table "P" and Divide by Pitch
SOLUTION : Ratio = 2 to 1
From Chart "P" Pinion addendum
for 1 Diametral Pitch = 1.350"
1.350÷ 12 = .1125
Pinion Addendum = .1125"
How to Find “Addendum for Gear”
RULE : Having Ratio Use Table "P" and Divide by Pitch
SOLUTION : Ratio = 2 to 1
From Chart "P" Gear Addendum for 1
Diametral Pitch = .650"
.650÷12 = .0541"
Gear Addendum = .0541"
How to Find “Dedendum of Pinion”
RULE : Divide 2.188 by the DP and Subtract the Addendum
SOLUTION : DP = 12
Addendum of Pinion = .1125"
(2.188÷12) - .1125 = .0698"
Pinion Dedendum = .0698"
How to Find “Dedendum of Gear”
RULE : Divide 2.188 by the DP and Subtract the Addendum
SOLUTION : DP = 12
Addendum of Gear = .0541"
(2.188÷12) - .0541 = .1282"
Gear Dedendum = .1282"
