Deep groove ball bearings for electric motors — CM reference range clearance chart
Look up unmounted radial clearance in micrometres by bearing family, bore size and clearance class. Includes cylindrical and tapered bore reference tables.
Find the unmounted clearance range
CM at 8 mm bore
No numerical range is published in this reference for that type, size and class. No adjacent range is substituted.
These are unmounted, theoretical radial clearances, not operating clearances or measured values under a test load. Fits and temperature differences change the working clearance. The manufacturer's exact product specification takes priority.
Complete Deep groove ball bearings for electric motors table
CM reference range · all clearance values in μm · — means not listed. Lower bounds are exclusive, except the explicitly marked 10 mm CM boundary.
| Nominal bore d (mm) | CM min–max (μm) |
|---|---|
| ≥ 10 to ≤ 18 | 4–11 |
| > 18 to ≤ 30 | 5–12 |
| > 30 to ≤ 50 | 9–17 |
| > 50 to ≤ 80 | 12–22 |
| > 80 to ≤ 120 | 18–30 |
| > 120 to ≤ 160 | 24–38 |
Enter the displayed minimum and maximum as the calculator's initial clearance. Supply the actual outside diameter, fit reductions and temperatures; those values are not inferred from the bore.
All seven reference tables
Deep groove ball bearings
21 bore bands · C2 / CN / C3 / C4 / C5
Open numerical chart →Cylindrical boreSelf-aligning ball bearings
14 bore bands · C2 / CN / C3 / C4 / C5
Open numerical chart →Tapered boreSelf-aligning ball bearings
14 bore bands · C2 / CN / C3 / C4 / C5
Open numerical chart →Cylindrical boreCylindrical roller and machined-ring needle bearings
21 bore bands · C2 / CN / C3 / C4 / C5
Open numerical chart →Cylindrical boreSpherical roller bearings
27 bore bands · C2 / CN / C3 / C4 / C5
Open numerical chart →Tapered boreSpherical roller bearings
26 bore bands · C2 / CN / C3 / C4 / C5
Open numerical chart →CM reference rangeDeep groove ball bearings for electric motors
6 bore bands · CM
Open numerical chart →CN, C3 and CM are not interchangeable labels
CN is the normal range; C2 is smaller, and C3, C4 and C5 are successively larger groups for the applicable bearing family. Ranges can overlap. CM is a special motor-ball-bearing reference range, not a universal synonym for CN. Ball, cylindrical-roller and spherical-roller tables must not be mixed.
Unmounted clearance → mounting reductions → thermal changes → operating clearance. A negative calculated operating result needs review; it is not automatically a valid preload setting.
Reference basis & limitations
JTEKT Basic Bearing Knowledge — Bearing internal clearance, Tables 10-2, 10-6, 10-7 (1), 10-8 (1), 10-9 (1) and (2). Reference data checked 1 October 2026. Product-specific drawings and current manufacturer requirements take priority.
BearingScope is an independent technical lookup service. Unknown values are not filled with estimates. These references do not certify interchangeability or application suitability.