Tolerance class P6 is the bearing dimensional and runout tolerance grade per ISO 492, one step above the standard P0 (Normal) class, equivalent to ABEC 5 in the ABMA system, and used for applications requiring moderate rotational precision — high-end pumps, precision industrial fans, and small servo motors.
The ISO precision scale for bearings: P0 (normal) → P6 → P5 → P4 → P2 (highest). The smaller the number, the tighter the tolerance. P6 means inner ring bore tolerance (Δdmp) is controlled approximately 30–40% tighter than P0, and inner ring radial runout (Kia) is reduced to 8–15 µm instead of 15–25 µm at P0.
An important distinction: P6 is not a "better P0" for every application. P0 is appropriate for 90% of standard industrial applications. P6 is necessary when speeds exceed 8,000 rpm, when vibration and noise are strict technical requirements, or when the bearing is part of a precision drive system such as a servo gearbox. See the full precision class comparison at bearing precision classes and browse deep groove ball bearings in P6 tolerance class.
P6 Tolerance Parameters vs. P0
P6 tolerances are controlled across three primary criteria: dimensional accuracy (inner and outer ring diameters), rotational accuracy (radial and axial runout), and raceway quality. For deep groove ball bearing 6205/P6 (d = 25, D = 52, B = 15 mm, C = 14.8 kN):
- Δdmp (inner bore tolerance): 0 / −8 µm (P0: 0 / −10 µm)
- Kia (inner ring radial runout): ≤ 5 µm (P0: ≤ 10 µm)
- Kea (outer ring radial runout): ≤ 6 µm (P0: ≤ 13 µm)
- Sd (face runout): ≤ 8 µm (P0: ≤ 15 µm)
| Parameter | P0 (Normal) | P6 | P5 |
|---|---|---|---|
| Δdmp — d = 18–30 mm | 0 / −10 µm | 0 / −8 µm | 0 / −6 µm |
| Kia (inner ring radial runout) | ≤ 10 µm | ≤ 5 µm | ≤ 4 µm |
| Kea (outer ring radial runout) | ≤ 13 µm | ≤ 6 µm | ≤ 5 µm |
| Suitable speed | < 8,000 rpm | 8,000–15,000 rpm | 15,000–25,000 rpm |
| Typical applications | General industry | Small servos, precision fans | Machine tool spindles |