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 |