Bearing Type Comparison
| Bearing Type | Radial load | Axial load | Speed capability | Misalignment tolerance | Typical applications |
|---|---|---|---|---|---|
| Deep groove ball (DGBB) | Medium | Low–medium (both directions) | High | Very low (<0.1°) | Electric motors, fans, light pumps, conveyor rolls |
| Angular contact ball (ACBB) — single row | Medium | High (one direction only) | High | Very low | Centrifugal pumps, spindles, paired/back-to-back mounting |
| Angular contact ball (ACBB) — double row | Medium | High (both directions) | High | Very low | Pumps, light gearboxes |
| Self-aligning ball | Medium | Low | High | Medium (±3°) | Applications with shaft deflection, agricultural equipment |
| Cylindrical roller (CRB) | High | None or low (depends on type) | Very high | Very low | Electric motors, gearboxes (non-locating position) |
| Tapered roller (TRB) | High | High (one direction per bearing) | Medium | Very low | Gearboxes, vehicle wheels, heavy shaft applications |
| Spherical roller (SRB) | Very high | Medium (both directions) | Medium | High (±2°) | Heavy fans, conveyor drives, crushers, rope drums |
| Needle roller | High | None | High | Very low | Limited space applications — reciprocating components, gearboxes |
| Thrust ball | None | High (one direction) | Low–medium | Very low | Vertical shaft end location, hoists |
| Spherical roller thrust | Low | Very high | Low | Medium | Vertical turbines, vertical fans, heavy axial loads |
Deep Groove Ball Bearings
The most widely used bearing type in industry. Single row DGBB (60-series, 62-series, 63-series) handles moderate radial loads and moderate axial loads in both directions. Available in open, shielded (Z), and sealed (RS/2RS) variants:
- Open: Requires external lubrication; for high-speed, high-temperature applications with circulating oil or regular regreasing
- Shielded (ZZ): Metal shields — some protection from dust; still greaseable from the sides. Standard for most motor and fan applications
- Sealed (2RS): Rubber contact seals — factory-filled with grease; not intended for regreasing. Used in small motors and inaccessible positions
Roller Bearings
Roller bearings have line contact rather than point contact, giving them higher radial load capacity than equivalent-sized ball bearings — typically 50–100% higher. Key types:
- Cylindrical roller (NU, N, NJ, NUP types): NU and N types are non-locating (no axial guidance); NJ and NUP types carry some axial load. Used as the free-end bearing in shaft systems to allow thermal expansion
- Tapered roller bearings: The taper geometry means they carry combined radial and axial loads simultaneously. Must be installed in opposing pairs (face-to-face or back-to-back). Require correct axial preload setting — too tight causes overheating; too loose causes axial play
- Spherical roller bearings: Two rows of barrel-shaped rollers running on a spherical outer raceway — gives self-aligning capability. The choice for heavy machinery with shaft deflection or housing misalignment
Locating vs Non-Locating Arrangements
Most shaft systems require one locating bearing (fixed-end, constrains axial movement) and one non-locating bearing (free-end, allows thermal expansion):
| Position | Typical bearing choice | Notes |
|---|---|---|
| Locating end (Drive end) | Deep groove ball (paired), angular contact ball pair, or cylindrical NU + thrust bearing | Axially constrained in housing; handles all axial load |
| Non-locating end (Non-drive end) | Cylindrical roller NU type, or DGBB in clearance housing | Outer ring free to slide axially; accommodates thermal growth |
Bearing Designation System
ISO bearing designations encode type, series, and bore diameter:
- First digits: Bearing type — 6 = deep groove ball; 7 = angular contact ball; NU/N/NJ = cylindrical roller; 2/3 = spherical roller; 3 = tapered roller (in ISO system)
- Second digit: Width and diameter series (e.g., 62XX = 02 series — medium width, medium OD; 63XX = heavier)
- Last two digits × 5 = bore in mm for bores 20–480 mm (e.g., 6210 = 50 mm bore; 6306 = 30 mm bore)
- Suffixes: C3 = extra clearance; ZZ = two shields; 2RS = two rubber seals; M = brass cage