SKF
Tolerances
Bearing tolerances define the permissible dimensional and running accuracy limits for bore diameter, outside diameter, width, and rotational precision. Standardized by ISO, these tolerance classes allow interchangeable use and predictable performance. Stricter tolerance grades provide higher rotational accuracy and reduced vibration — critical for machine tool spindles, electric motors, and precision instruments. SKF manufactures bearings across a range of tolerance classes, from Normal to P2 and ABEC 9 for super-precision applications. Proper matching of bearing tolerances with shaft and housing fits ensures optimal internal clearance after mounting. Understanding tolerance specifications helps design engineers achieve the required shaft guidance, noise levels, and service life. SKF catalogs clearly list dimensional tolerances, making it simple to verify compatibility during design or replacement specification.
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ISO/DIN Tolerance Standards
Bearings compliant with globally recognized classes for seamless integration.
Precision Classes for Sensitive Applications
P5, P4, P2, and ABEC grades for spindles and metrology equipment.
Improved Rotational Accuracy
Tighter tolerances reduce runout and vibration, extending connected component life.
Predictable Post-Mounting Clearance
Matched tolerances with fits ensure proper internal clearance under load.
Simplified Quality Control
Clearly defined limits facilitate incoming inspection and supplier qualification.
Application-Matched Options
Select normal tolerances for general machinery, or precision grades where needed.
ISO Tolerance Classes for Bearings: Normal, P6, P5, P4, P2
Normal (P0) tolerance is sufficient for most industrial applications. P6 offers reduced dimensional variation, while P5 and P4 are preferred for machine tools and high-speed electric motors. P2 is the highest precision, used in aerospace and metrology. Choosing the correct class prevents unnecessary costs and ensures adequate guidance and accuracy.
How Bearing Tolerances Affect Machine Vibration and Life
Excessive runout or poor dimensional accuracy increases vibration and uneven load distribution, accelerating fatigue. For motors with variable frequency drives, tighter tolerances reduce electrical erosion risk by maintaining consistent air gaps and reducing shaft currents. Correct tolerance selection is a cost-effective way to boost reliability.