Bearing internal clearance charts & numerical lookup
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
C3 at 8 mm bore
Bore band: > 6 to ≤ 10 mm. JTEKT Table 10-2.
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.
Compare clearance classes at 8 mm
Each bar spans a permitted minimum–maximum range, starting from the same zero. Overlapping ranges do not make two classes interchangeable; the complete specified range matters.
- C20–7 μm
- CN2–13 μm
- C38–23 μmSelected
- C414–29 μm
- C520–37 μm
JTEKT Table 10-2 · Deep groove ball bearings / Cylindrical bore. This compares catalogue limits, not measurements from an individual bearing and not a recommended class.
Complete Deep groove ball bearings table
Cylindrical bore · all clearance values in μm · — means not listed. Lower bounds are exclusive, except the explicitly marked 10 mm CM boundary.
| Nominal bore d (mm) | C2 min–max (μm) | CN min–max (μm) | C3 min–max (μm) | C4 min–max (μm) | C5 min–max (μm) |
|---|---|---|---|---|---|
| > 2.5 to ≤ 6 | 0–7 | 2–13 | 8–23 | 14–29 | 20–37 |
| > 6 to ≤ 10 | 0–7 | 2–13 | 8–23 | 14–29 | 20–37 |
| > 10 to ≤ 18 | 0–9 | 3–18 | 11–25 | 18–33 | 25–45 |
| > 18 to ≤ 24 | 0–10 | 5–20 | 13–28 | 20–36 | 28–48 |
| > 24 to ≤ 30 | 1–11 | 5–20 | 13–28 | 23–41 | 30–53 |
| > 30 to ≤ 40 | 1–11 | 6–20 | 15–33 | 28–46 | 40–64 |
| > 40 to ≤ 50 | 1–11 | 6–23 | 18–36 | 30–51 | 45–73 |
| > 50 to ≤ 65 | 1–15 | 8–28 | 23–43 | 38–61 | 55–90 |
| > 65 to ≤ 80 | 1–15 | 10–30 | 25–51 | 46–71 | 65–105 |
| > 80 to ≤ 100 | 1–18 | 12–36 | 30–58 | 53–84 | 75–120 |
| > 100 to ≤ 120 | 2–20 | 15–41 | 36–66 | 61–97 | 90–140 |
| > 120 to ≤ 140 | 2–23 | 18–48 | 41–81 | 71–114 | 105–160 |
| > 140 to ≤ 160 | 2–23 | 18–53 | 46–91 | 81–130 | 120–180 |
| > 160 to ≤ 180 | 2–25 | 20–61 | 53–102 | 91–147 | 135–200 |
| > 180 to ≤ 200 | 2–30 | 25–71 | 63–117 | 107–163 | 150–230 |
| > 200 to ≤ 225 | 2–35 | 25–85 | 75–140 | 125–195 | 175–265 |
| > 225 to ≤ 250 | 2–40 | 30–95 | 85–160 | 145–225 | 205–300 |
| > 250 to ≤ 280 | 2–45 | 35–105 | 90–170 | 155–245 | 225–340 |
| > 280 to ≤ 315 | 2–55 | 40–115 | 100–190 | 175–270 | 245–370 |
| > 315 to ≤ 355 | 3–60 | 45–125 | 110–210 | 195–300 | 275–410 |
| > 355 to ≤ 400 | 3–70 | 55–145 | 130–240 | 225–340 | 315–460 |
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.
Three questions a clearance suffix cannot answer
Is C3 a tighter manufacturing tolerance?
No. C3 is an internal-clearance group. An ABEC or ISO precision class controls specified dimensional and running-accuracy limits; a shaft fit describes two mating surfaces. Keep these as separate fields when comparing records.
Precision, clearance and fits →Does C3 or C4 specify a maximum speed?
No RPM value follows from either suffix alone. A higher-clearance group may compensate for mounting or thermal reductions, but that does not make it a high-speed upgrade. Use the exact bearing's speed evidence and the complete operating conditions.
C3 versus C4 selection checks →Can a shaft or housing gap use this table?
No. These rows describe relative movement inside an unmounted rolling bearing. They are not journal-bearing oil clearances, housing machining tolerances, feeler-gauge instructions or a preload setting.
Shaft and housing fit reference →Read the three states in order
- Before mountingIdentify bearing family, bore construction, nominal bore and the complete clearance designation. Use its full interval, not a midpoint presented as an exact measurement.
- After mountingRing expansion and compression can reduce clearance. Seat interference does not transfer one-for-one into raceway movement.
- During operationTemperature differences and load change the result further. A measured value needs the manufacturer's measurement method and correction; do not compare it blindly with an unloaded theoretical range.
A larger initial group is useful only when the resulting operating range is suitable for the actual arrangement. More internal play is not a general quality ranking.
Why do some class ranges overlap?
A group is an interval, not one fixed gap. For example, in this JTEKT deep-groove table at a 25 mm bore, CN is 5–20 μm and C3 is 13–28 μm. Their overlap is 13–20 μm (0.013–0.020 mm), but their minimum and maximum limits differ. A value inside both ranges does not identify the original class or authorize a substitution.
How should I read a band boundary or an empty cell?
For a row labelled “over 24 to 30”, 24 mm is excluded and 30 mm is included. The explicitly marked CM lower boundary is an exception. An empty range means the source has no value for that combination; it is not zero, and the tool does not borrow a neighbouring band.
Can this chart be used as an SKF, NSK or Timken certificate?
No. Its data source is JTEKT and its bearing-family scope is stated. Another manufacturer's special specification or an exact product drawing may differ. A comparable designation does not turn this reference into evidence for another brand's exact product.
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.