What Is Cấp chính xác P5? — Bearing Glossary

Tolerance class P5 is the bearing tolerance grade per ISO 492, one step above P6 and equivalent to ABEC 7 in the ABMA system, used for machine tool spindles, high-speed servo motors, and industrial measuring equipment requiring inner ring radial runout below 4 µm.

In the scale P0 → P6 → P5 → P4 → P2, P5 marks the transition from "high precision" to "ultra-high precision". Inner ring radial runout (Kia) at P5 is ≤ 4 µm, compared to ≤ 5 µm at P6 and ≤ 10 µm at P0. See all precision grades compared at bearing precision classes and choose deep groove ball bearings in P5 tolerance for CNC spindle applications. That seems close, but at 15,000–25,000 rpm, 1 µm of runout generates an unbalanced centrifugal force that directly affects machining quality.

P5 imposes stricter requirements on raceway quality and ball surface finish. P5 bearings must be manufactured in cleanroom conditions, with 100% individual unit inspection — not batch sampling as with P0 or P6.

P5 Applications and Selection

P5 appears most frequently in three domains. First, CNC milling and high-speed turning spindles — speeds of 10,000–25,000 rpm with workpiece surface finish requirements of Ra ≤ 0.4 µm. Second, servo motors rated 0.5–5 kW in industrial robots and high-speed packaging machines. Third, guide rollers in precision printing presses and precision rolling machines.

Practical example: bearing 6205/P5 (d = 25, D = 52, B = 15 mm, C = 14.8 kN) mounted in a mini CNC milling spindle. Total spindle runout measured at the tool tip equals bearing runout plus fitting error. With P5, bearing runout is ≤ 4 µm; with P0 it is ≤ 10 µm — the 6 µm difference directly affects contour accuracy at the ±5 µm tolerance the machine guarantees.