Metric Tolerances
ANSI Standard Limits and Fits
The following fit types are in accordance with the ANSI B4.2-1978 (R2004) standard.
| Hole Basis | Shaft Basis | Fit |
|---|---|---|
| H11/c11 | C11/h11 | Loose running |
| H9/d9 | D9/h9 | Free running |
| H8/f7 | F8/h7 | Close running |
| H7/g6 | G7/h6 | Sliding |
| H7/h6 | H7/h6 | Locational clearance |
| H7/k6 and H7/n6 | K7/h6 and N7/h6 | Locational transition |
| H7/p6 | P7/h6 | Locational interference |
| H7/s6 | S7/h6 | Medium drive |
| H7/u6 | U7/h6 | Force |
Tolerance Designation
A Metric fit is specified by stating the fundamental deviation and the IT#. Remember!
- IT# = the amount that the dimension can vary (tolerance zone size).
- Fundamental deviation (letter) = establishes the position of the tolerance zone with respect to the basic size. Hole = upper case Shaft = lower case
Fits are specified by using the:
- fundamental deviation (letter)
- IT# (International Tolerance Grade #).
When specifying the fit:
- The hole = upper case letter
- The shaft = lower case letter