Involute Spline ANSI B92.1 Equations and Design

Gear Design and Engineering

American National Standard Involute Splines - These splines or multiple keys are similar in form to internal and external involute gears. In general manufacturing external splines is facilitated either by hobbing, rolling, or on a gear shaper, and internal splines either by broaching or on a gear shaper. The internal spline is held to basic dimensions and the external spline is varied to control the fit. Involute splines have maximum strength at the base, can be accurately spaced and are self-centering, thus equalizing the bearing and stresses, and they can be measured and fitted accurately.

Involute Spline Basic Dimensions

Equations for Involute Spline Basic Dimensions ANSI B92.1-1970, R1993

Term
Symbol
30 deg φD
37.5 deg φD
45 deg φD
Flat Root Side Fit
Flat Root Major Dia Fit
Fillet Root Side Fit
Fillet Root Side Fit
Fillet Root Side Fit
2.5/ 5 - 32/ 64 Pitch
3 /6 - 16 /32 Pitch
2.5/ 5 - 48/ 96 Pitch
2.5/ 5 - 48/ 96 Pitch
10/ 20 - 128/ 256 Pitch
Stub Pitch
Ps
2P
2P
2P
2P
2P
Pitch Diameter
D
N/P
N/P
N/P
N/P
N/P
Base Diameter
Db
D cos φD
D cos φD
D cos φD
D cos φD
D cos φD
Circular Pitch
p
π/P
π/P
π/P
π/P
π/P
Minimum Effective Space Width
sv
π/(2P)
π/(2P)
π/(2P)
(0.5π + 0.1) / P
(0.5π + 0.1) / P
Major Diameter, Internal
Dri
(N + 1.35)/P
(N + 1)/P
(N + 1.8)/P
(N + 1.6)/P
(N + 1.4)/P
Major Diameter, External
Do
(N + 1)/P
(N + 1)/P
(N + 1)/P
(N + 1)/P
(N + 1)/P
Minor Diameter, Internal
Di
(N - 1 )/ P
(N - 1 )/ P
(N - 1 )/ P
(N - 0.8 )/ P
(N - 0.8 )/ P
Minor Dia. Ext.
2.5/5 thru 12/ 24 pitch
Dre
(N - 1.35)/ P
(N - 1.8)/ P
(N - 1.3)/ P
16/ 32 pitch and finer
(N - 1.2)/ P
10/ 20 pitch and finer
(N - 1 )/ P
Form Diameter, Internal
DFi
(N + 1) / P + 2cF
(N + 0.8) / P - 0.004 + 2cF
(N + 1) / P + 2cF
(N + 1) / P + 2cF
(N + 1) / P + 2cF
Form Diameter, External
DFe
(N - 1)/ P - 2cF
(N - 1)/ P - 2cF
(N - 1)/ P - 2cF
(N - 0.8)/ P - 2cF
(N - 0.6)/ P - 2cF
Form Clearance (Radial)
cF
0.001 D, with max of 0.010, min of 0.002
 

π = 3.1415927

Note: All spline specification table dimensions in the standard are derived from these basic formulas by application of tolerances.

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