What are bearing tolerance classes?

Bearing tolerance classes define the dimensional and running accuracy of rolling bearings per ISO 492. Classes range from P0 (normal, least precise) to P2 (most precise). Higher precision means tighter tolerances on bore, OD, width, and runout.

What is the relationship between ISO and ABEC classes?

ISO P0 = ABEC 1, ISO P6 = ABEC 3, ISO P5 = ABEC 5, ISO P4 = ABEC 7, ISO P2 = ABEC 9. The ABEC system (Annular Bearing Engineering Committee) is used primarily in North America.

When should I use P6 or higher precision?

P6 is used for machine tool spindles (general), electric motors requiring low vibration, and precision gearboxes. P5 is for high-speed spindles. P4 and P2 are for ultra-precision applications like grinding spindles and gyroscopes.

Does tolerance class affect bearing life?

Tolerance class does not directly affect the rated life L10. However, higher precision bearings run smoother with less vibration, which can improve actual service life by reducing dynamic loads and improving lubrication conditions.

Are tolerance values the same for all bearing types?

ISO 492 covers radial bearings (ball and roller). Thrust bearings follow ISO 199. The tolerance values depend on the bearing bore diameter range and the selected class. Values shown here are for standard radial bearings.

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Bearing Tolerance Class Lookup

Look up bore, OD, and width tolerances per ISO 492 for tolerance classes P0 through P2 (ABEC 1–9). Enter bore diameter and select class.

ISO 492P0–P2 / ABEC 1–9μm Tolerances

Tolerances

Bore Tolerance Δdmp

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OD Tolerance ΔDmp

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Bore Variation Vdp

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Class & ABEC Equivalent

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ISO / ABEC Equivalence

ISO Class	ABEC	Typical Application
P0 (Normal)	ABEC 1	General machinery, fans, pumps, motors
P6	ABEC 3	Machine tools (general), electric motors (low vibration)
P5	ABEC 5	High-speed spindles, precision gearboxes
P4	ABEC 7	Grinding spindles, high-precision instruments
P2	ABEC 9	Ultra-precision spindles, gyroscopes

Bore Tolerance Δdmp (μm) — Selected Ranges

Bore Range (mm)	P0	P6	P5	P4	P2
10–18	0 / −8	0 / −7	0 / −5	0 / −4	0 / −2.5
18–30	0 / −10	0 / −8	0 / −6	0 / −5	0 / −2.5
30–50	0 / −12	0 / −10	0 / −8	0 / −6	0 / −2.5
50–80	0 / −15	0 / −12	0 / −9	0 / −7	0 / −4
80–120	0 / −20	0 / −15	0 / −10	0 / −8	0 / −5
120–180	0 / −25	0 / −18	0 / −13	0 / −10	0 / −7

ℹ️ Note: Tolerances are always negative (below nominal). The bearing bore is manufactured at or slightly below the nominal dimension.

Bearing Tolerance Class Lookup | ISO 492 | P0 P6 P5 P4 P2 | Free Online Tool

Published by admin on February 15, 2026 February 15, 2026

Tolerances

ISO / ABEC Equivalence

Bore Tolerance Δdmp (μm) — Selected Ranges