Understanding Bearing Clearance

A technical guide to selecting the right internal clearance for standard and miniature deep groove ball bearings.


Bearing Clearance Overview

Bearing Clearance (or internal clearance) refers to the total distance by which one bearing ring can be moved relative to the other in either the radial direction (Radial Clearance) or the axial direction (Axial Clearance)[cite: 5, 6].

Proper selection of bearing clearance is a critical factor influencing bearing performance, including operating life, noise, vibration, and heat generation[cite: 5, 6].

Standard standard-sized deep groove ball bearings (bore diameter d ≥ 10mm) utilize the standard ISO/GB clearance groups ranging from C2 (tightest) to CN (normal), and up to C3, C4, and C5 (looser)[cite: 5, 6]. Conversely, miniature bearings (outer diameter D < 9mm and bore diameter d < 10mm) follow the MC system, spanning from MC1 up to MC6[cite: 5, 6].

Selecting the ideal clearance requires a balance of operating conditions:

  • Normal Clearance (CN / MC3): The default factory setting used for general electrical motors and standard applications[cite: 5, 6].
  • Tight Clearance (C2 / MC1 / MC2): Ideal for high-precision oscillatory parts, low-noise drives, or applications requiring high rigidity where play must be minimized[cite: 5, 6].
  • Loose Clearance (C3 / C4 / C5 / MC4 / MC5 / MC6): Essential for high-speed rotations, large temperature differentials (to compensate for thermal expansion), or heavy shaft interference fits[cite: 5, 6].

1. Standard Deep Groove Ball Bearing Clearance Table

For standard-sized deep groove ball bearings with a nominal bore diameter d ≥ 10mm (e.g., 6200, 6300 series)[cite: 5, 6].

Unit: Micrometers (μm)[cite: 5, 6]

Nominal Bore d (mm)
Over — Incl.		 C2 CN (Normal) C3 C4 C5
Min Max Min Max Min Max Min Max Min Max
10 — 18 0 9 3 18 11 25 18 33 25 45
18 — 24 0 10 5 20 13 28 20 36 28 48
24 — 30 1 11 5 20 13 28 23 41 30 53
30 — 40 1 11 6 20 15 33 28 46 40 64
40 — 50 1 11 6 23 18 36 30 51 45 73
50 — 65 1 15 8 28 23 43 38 61 55 90
65 — 80 1 15 10 30 25 51 46 71 65 105

2. Miniature Deep Groove Ball Bearing Clearance Table

For miniature deep groove ball bearings with an outer diameter D < 9mm or bore diameter d < 10mm (MC system)[cite: 5, 6].

Unit: Micrometers (μm)[cite: 5, 6]

Code Description Range Typical Applications
MC1 Extra Tight 0 — 5 High-precision oscillatory parts, no-play instruments.
MC2 Tight 3 — 8 Low-noise applications, precision drives with slight preload.
MC3 (Normal) Standard (CN eq.) 5 — 10 Default factory group, primary choice for general electrical motors.
MC4 Loose 8 — 13 Medium to high speeds, or significant shaft interference fits.
MC5 Extra Loose 13 — 20 High speeds, large ΔT to compensate thermal expansion (e.g. drone motors).
MC6 Super Loose 20 — 28 Special high-temp environments or heavy interference fits.