| Characteristic of Support | Face width (in) | |||
| 0 to 2 | 6 | 9 | 16 up | |
| Accurate mountings, small bearing clearances, minimum deflection, precision gears | 0.3 | 0.4 | 1.5 | 1.8 | 
| Less rigid mountings, less accurate gears, contact across full face | 1.6 | 1.7 | 1.8 | 2.2 | 
| Accuracy and mounting such that less than full-face contact exists | over 2.2 | |||