Formulas for dimensions and tolerances for fit classes
|
Term |
Symbol |
Formula |
EDP representation |
|
Pitch diameter |
D |
m z |
D |
|
Base diameter |
D b |
m z cos αD |
DB |
|
Circular pitch |
p b |
m π cos αD |
PB |
|
Fundamental deviation, external |
es v |
Resulting from external deviation k, js, h, f, e, d |
ESV |
|
Minimum major diameter, internal: 30 deg, flat root 30 deg, fillet root 37.5 deg, fillet root 45 deg, fillet root |
D ei mim D ei mim D ei mim D ei mim |
m (z + 1.5) m (z + 1.8) m (z + 1.4) m (z + 1.2) |
DEIMIM DEIMIM DEIMIM DEIMIM |
|
Maximum major diameter, external |
D ei min |
D ei max + (T + λ)/tan α D - see Note 1 |
DEIMAX |
|
Minimum form diameter, internal: 30 deg, flat root, and fillet root 37.5 deg, fillet root 45 deg, fillet root |
D Fi mim D Fi mim D Fei mim |
m (z + 1) + 2 c f m (z + 0.9) + 2 c f m (z + 0.8) + 2 c f |
DFEIMIM DFIMIM DFIMIM |
|
Minimum minor diameter, internal |
D ii min |
D Fe max + 2 c F - see Note 2 |
DIIMIN |
|
Maximum minor diameter, internal: m ≤ 0.75 0.75< m< 2 m => 2 |
D ii max D ii max D ii max |
D ii max + IT 10 ii max + IT 11 ii max + IT 12 |
DIIMAX DIIMAX DIIMAX |
|
Basic space width |
E |
0.5 π m |
E |
|
Minimum effective space width |
E v min |
0.5 π m |
EVMIN |
|
Maximum actual space width class 4 class 5 class 6 class 7 |
E max E max E max E max |
E v min + (T + λ) E v min + (T + λ) E v min + (T + λ) E v min + (T + λ) |
EMAX EMAX EMAX EMAX |
|
Minimum actual space width |
E min |
E v min + λ |
EMIN |
|
Maximum effective space width |
E v max |
E v min + T v |
EVMAX |
|
Maximum major diameter, external 30 deg, flat root, and fillet root 37.5 deg, fillet root 45 deg, fillet root |
D ee max D ee max D ee max |
m (z + 1) + es v /tan α D - see Note 3 m (z + 0.9) + es v /tan α D - see Note 3 m (z + 0.8) + es v /tan α D - see Note 3 |
DEEMAX DEEMAX DEEMAX |
|
Minimum minor diameter, external: m ≤ 0.75 0.75< m< 2 m => 2 |
D ee min D ee min D ee min |
D ee min - IT 10 ee min - IT 11 ee min - IT 12 |
DEEMIN DEEMIN DEEMIN |
|
Maximum form diameter |
D Fe max |
|
DFEMAX |
|
Maximum minor diameter, external 30 deg, flat root 30 deg, fillet root 37.5 deg, fillet root 45 deg, fillet root |
D that is, max D that is, max D that is, max D that is, max |
m (z - 1.5) + es v /tan α D m (z - 1.8) + es v /tan α D m (z - 1.4) + es v /tan α D m (z - 1.2) + es v /tan α D |
DIEEMAX DIEMAX DIEMAX DIEMAX |
|
Minimum minor diameter, external |
D that is, max |
D that is, max - (T + λ / tan α D |
DIEMIN |
|
Basic tooth thickness |
S |
0.5 π m |
S |
|
Maximum effective tooth thickness |
S v max |
S + es V |
SVMAX |
|
Minimum actual tooth thickness class 4 class 5 class 6 class 7 |
S min S min S min S min |
S v max - (T + λ) S v max - (T + λ) S v max - (T + λ) S v max - (T + λ) |
SMIN SMIN SMIN SMIN |
|
Maximum actual tooth thickness |
S max |
S v max - λ |
SMAX |
|
Minimum effective tooth thickness |
S min |
S v max - λ |
SVMIN |
|
Maximum effective clearance |
c v max |
E v max - S v max |
CVMAX |
|
Minimum effective clearance |
c v min |
E v min - S v mim |
CVMIN |
|
Note 1 |
T + λ for class 7 |
|
Note 2 |
For all classes of fit, always take the D Fe max value corresponding to the H/h fit. |
|
Note 3 |
Take e sv = 0 for fundamental deviation js and k. |