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 Wire
Measurements		 INTERNAL SPUR GEARS

Determining Dimension under Pins
TO GET HAVING RULE FORMULA
N Number of teeth Given 12
DP Diametral pitch 24
α Pressure angle 14.5
s Arc space width 0.06800
d Pin diameter 0.06701
PD Pitch diameter N/DP 0.50000
BD Base diameter PD•COS(α) 0.48407
A   s/PD 0.13600
D   d/BD 0.13843
INVα Involute function of α TAN(α)-[α(π/180)] 0.00554
INVβ   A+INVα-D 0.00312
β Pressure angle to pin center see tables page (G14) 11.00809
CC Twice the center distance of pin and gear BD/COS(β) 0.49488
DE Dimension under pins even # of teeth CC-d 0.42787
DO Dimension under pins odd # of teeth CC•COS(90/N)-d ***************
Φ Pressure angle to point of tangency TAN(Φ)=TAN(β)+D 19.33857
RT Radius to point of tangency BD/[2•COS(Φ)] 0.25651

Determining Arc Space Width Given Dimensions under Pins
TO GET HAVING RULE FORMULA
N Number of teeth Given 44
DP Diametral pitch 24
α Pressure angle 14.5
d Pin diameter 0.06701
DE Dimension under pins even # of teeth 1.76152
DO Dimension under pins odd # of teeth **********
PD Pitch diameter N/DP 1.83333
BD Base diameter PD•COS(α) 1.77494
CE Twice the center distance of pin and gear even # of teeth DE+d 1.82853
CO Twice the center distance of pin and gear odd # of teeth (DO+d)/COS(90/N) **********
β Pressure angle to pin center COS(β)=BD/CE or CO 13.90611
INVβ Involute function of b TAN(β)-[β(π/180)] 0.00488
D   d/BD 0.03775
INVα Involute function of α TAN(α)-[α(π/180)] 0.00554
s Arc space width PD(INVβ+D-INVα) 0.06800