Table 2. Formulas for Involute Spline Basic Dimensions ANSI B92.1-1996
37.5 deg φ D
45 deg φ D
30 deg φ D
Flat Root Side Fit 2.5 ∕ 5–32 ∕ 64 Pitch
Flat Root Major Dia Fit
Fillet Root Side Fit 2.5 ∕ 5–48 ∕ 96 Pitch
Fillet Root Side Fit 2.5 ∕ 5–48 ∕ 96 Pitch
Fillet Root Side Fit 10 ∕ 20–128 ∕ 256 Pitch
3 ∕ 6–16 ∕ 32 Pitch
Term
Symbol
2 P
2 P
2 P
2 P
2 P
Stub Pitch
P s D
Pitch Diameter Base Diameter Circular Pitch
N ⁄ P
N ⁄ P
N ⁄ P
N ⁄ P
N ⁄ P
D cos φ D
D cos φ D
D cos φ D
D cos φ D
D cos φ D
D b
π ⁄ P
π ⁄ P
π ⁄ P
π ⁄ P
π ⁄ P
p
Minimum Effective Space Width Major Diameter, Internal Major Diameter, External Minor Diameter, Internal
π ⁄ (2 P )
π ⁄ (2 P )
π ⁄ (2 P )
(0.5 π + 0.1) ⁄ P
(0.5 π + 0.2) ⁄ P
s v
( N + 1.35) ⁄ P
( N + 1) ⁄ P ( N + 1) ⁄ P ( N - 1) ⁄ P
( N + 1.8) ⁄ P ( N + 1) ⁄ P ( N - 1) ⁄ P ( N - 1.8) ⁄ P ( N - 2) ⁄ P
( N + 1.6) ⁄ P ( N + 1) ⁄ P ( N - 0.8) ⁄ P
( N + 1.4) ⁄ P ( N + 1) ⁄ P ( N - 0.6) ⁄ P
D ri D o
( N + 1) ⁄ P ( N - 1) ⁄ P
D i
2.5 ∕ 5 thru 12 ∕ 24 pitch 16 ∕ 32 pitch and finer 10 ∕ 20 pitch and finer
…
Minor Dia. Ext.
( N - 1.35) ⁄ P
( N - 1.3) ⁄ P
D re
…
( N - 1) ⁄ P
Form Diameter, Internal Form Diameter, External Form Clearance (Radial)
( N + 1) ⁄ P - 2 cF ( N - 1) ⁄ P - 2 cF
( N + 0.8) ⁄ P - 0.004 + 2 cF
( N + 1) ⁄ P + 2 cF ( N - 1) ⁄ P - 2 cF
( N + 1) ⁄ P + 2 cF ( N − 0.8) ⁄ P - 2 cF
( N + 1) ⁄ P + 2 cF ( N - 0.6) ⁄ P - 2 cF
D Fi D Fe
( N - 1) ⁄ P - 2 cF
0.001 D , with max of 0.010, min of 0.002
c F
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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