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The Cornerstone of Precision and Lifespan: In-Depth Understanding of Bearing Clearance and Tolerance Grades

2025-11-19

When selecting bearings, "clearance" and "precision grade" are two crucial yet easily confused technical parameters. Together, they define the bearing's "character" and directly affect the equipment's operational performance.

What is Clearance?

Clearance, simply put, refers to the "gap" existing inside the bearing (between the rolling elements and the raceway). It's not necessarily better the smaller it is; it needs to be precisely selected based on the application scenario.

C1/C2 Group: Small or micro-clear clearance, suitable for applications requiring extremely high rotational precision and low vibration.

C0 Group (Standard Group): The most commonly used clearance, suitable for general operating conditions.

C3/C4/C5 Group: Increasingly larger clearances, typically used in applications requiring large temperature differences (such as metallurgical equipment) or heavy loads and impact loads to prevent clearance loss due to thermal expansion and subsequent "seizing."

What is Tolerance Grade? Tolerance grades measure the degree of deviation between the dimensional accuracy (such as inner diameter, outer diameter, and width) and rotational accuracy (such as the lateral runout of the inner raceway) of a bearing and its ideal values. Common grades from low to high are: P0 (standard grade), P6, P5, P4, and P2.

P0 grade: Widely used in conventional rotating machinery.

P4/P2 grades: Belong to ultra-precision grades, mainly used in high-precision machine tool spindles, aerospace, and other extremely precise fields. The higher the grade, the higher the bearing's limiting speed, and the lower the vibration and noise.

Summary: Clearance relates to "suitability," ensuring the bearing can operate flexibly without jamming in specific working environments; tolerance grade relates to "precision," determining the accuracy and smoothness of the bearing's rotation. Correctly understanding and matching these two is key to equipment reliability.