ISO 5753-1 — Radial internal clearance
The clearance table behind every bearing page here: how much radial play a deep groove ball bearing of a given bore is allowed, before it is fitted.
What it fixes
Radial internal clearance is the total distance one ring can be moved relative to the other, radially, with the bearing under no external load. ISO 5753-1 gives the permitted range for that movement, split into groups. The groups matter because clearance is not a quality grade — it is a fit decision. An interference fit on the shaft expands the inner ring and consumes clearance, and a hot inner ring expands more than a cool outer ring, so a bearing that is correct on the bench can be tight in service.
Radial internal clearancemicrometres, before mounting, for radial contact groove ball bearings
| Bore d (mm) | C2 | CN | C3 | C4 | C5 |
|---|---|---|---|---|---|
| over 2.5 to 6 | 0 to 7 | 2 to 13 | 8 to 23 | 14 to 29 | 20 to 37 |
| over 6 to 10 | 0 to 7 | 2 to 13 | 8 to 23 | 14 to 29 | 20 to 37 |
| over 10 to 18 | 0 to 9 | 3 to 18 | 11 to 25 | 18 to 33 | 25 to 45 |
| over 18 to 24 | 0 to 10 | 5 to 20 | 13 to 28 | 20 to 36 | 28 to 48 |
| over 24 to 30 | 1 to 11 | 5 to 20 | 13 to 28 | 23 to 41 | 30 to 53 |
| over 30 to 40 | 1 to 11 | 6 to 20 | 15 to 33 | 28 to 46 | 40 to 64 |
| over 40 to 50 | 1 to 11 | 6 to 23 | 18 to 36 | 30 to 51 | 45 to 73 |
| over 50 to 65 | 1 to 15 | 8 to 28 | 23 to 43 | 38 to 61 | 55 to 90 |
| over 65 to 80 | 1 to 15 | 10 to 30 | 25 to 51 | 46 to 71 | 65 to 105 |
| over 80 to 100 | 1 to 18 | 12 to 36 | 30 to 58 | 53 to 84 | 75 to 120 |
| over 100 to 120 | 2 to 20 | 15 to 41 | 36 to 66 | 61 to 97 | 90 to 140 |
The ranges are written as pairs: the lower figure is the minimum and the upper is the maximum. These are pre-mounting values for an unmounted bearing, measured without load or measurement forces. Fitting and temperature change them, and usually in one direction — downwards.
The five groupsfrom tightest to loosest
- C2
- Tighter than the default. Used where the fit already takes up most of the clearance, or where radial play must be kept small.
- CN (normal)
- The default. Usually not marked on the bearing at all — if the designation carries no clearance suffix, it is this group.
- C3
- Looser than the default. The common choice for interference fits on the shaft, for electric motors, and wherever the inner ring runs hotter than the outer ring.
- C4
- Looser again. For heavy interference fits and high-temperature service, where thermal expansion would otherwise close the fit up.
- C5
- The loosest group in the table. Special applications only.
The groups overlap, and that is not an error
Read down any row and the top of one group sits above the bottom of the next: at a 20 mm bore the CN range starts at 5 µm while C2 reaches 10 µm. That overlap is how the standard is written. It looks like a mistake to anyone who expects the groups to partition the range, and writing them out as non-overlapping would mean changing the values to make a tidier table.
The table above is one of six
ISO 5753-1 gives clearance values for six bearing types — radial contact groove ball bearings, double-row self-aligning ball bearings, cylindrical roller bearings, needle roller bearings, toroidal roller bearings and double-row self-aligning roller bearings — with cylindrical bore, plus tapered bore for four of them. Each type has its own table, and the numbers differ between them. The table on this page is the radial contact groove ball bearing one, because that is the only type tabulated in this library. Comparing a figure here with a figure quoted for a needle roller bearing will not agree, and the discrepancy is in the two tables being different, not in either being wrong.