Involute Spline Names, Symbols, and Relations for ANSI Standard

Term

Symbol

30 deg φ D

37.5 deg φ D

45 deg φ D

Flat Root Side Fit

 

Flat Root Majot 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 - 48/964 Pitch

2.5/5 - 48/96 Pitch

10/20 - 128/256 Pitch

Stub Pitch

P s

2P

 

2P

2P

2P

2P

Pitch Diameter

D s

N/P

 

N/P

N/P

N/P

N/P

Base Diameter

D b s

D coc φ D

 

D cos φ D

D cos φ D

D coc φ D

D coc φ D

Circular Pitch

p s

π/P

 

π/P

π/P

π/P

π/P

Minimum Effectice Space Width

s v s

π/(2P)

 

π/(2P)

π/(2P)

(0.5 π + 0.1)/P

(0.5 π + 0.2)/P

Major Diameter, Internal

D ri s

(N + 1.35)/P

 

(N + 1)/P

(N + 1.8)/P

(N + 1.6)/P

(N + 1.4)/P

Major Diameter, External

D o s

(N + 1)/P

 

(N + 1)/P

(N + 1)/P

(N + 1)/P

(N + 1)/P

Minor Diameter, Internal

D i s

(N - 1)/P

 

(N - 1)/P

(N - 1)/P

(N - 0.8)/P

(N - 0.6)/P

Minor Dia. Ext.

2.5/5 thru 12/24 Pitch

D re

(N - 1.35)/P

(N - 1.8)/P

(N - 1.3)/P

...

16/32 Pitch and finer

(N - 2)/P

10/20 Pitch and finer

...

(N - 1)/P

Form Diameter, Internal

D Fi

(N + 1)/P + cF

 

(N + 1)/P - 0.004 + 2cF

(N + 1)/P + 2cF

(N + 1)/P + 2cF

(N + 1)/P + 2cF

Form Diameter, External

D Fe

(N - 1)/P - cF

 

(N - 1)/P - 2cF

(N - 1)/P - 2cF

(N - 0.8)/P - 2cF

(N - 0.6)/P - 2cF

Form Clearance, Radial

c F

0.001 D, with max of 0.010, min of 0.002