30FC21120 bearings ( 150 mm x 210 mm x 120 mm) have the advantages of Extremely high radial load capacity, high rigidity, separable design, and are therefore widely used in the metallurgical rolling mills, large gearboxes, and heavy-duty extrusion presses.

| Part Number | 30FC21120 |
| Interchangeable | KOYO 30FC21120 |
| Desgin Figure | 2-2 |
| Cage | Machined brass cage |
| Radial internal clearance | C3 |
| Seal | Open |
| Bearing Type | Four-row cylindrical roller bearing for cold rolling mill, hot rolling mill, billet mill |
| Design type | Outer ring with rib, Two inner rings |
| Bearing Weight [lb] | 28.219 |
| d φ Inside [inch] | 5.905 |
| D Φ Outside [inch] | 8.268 |
| B Width [inch] | 4.724 |
| Fw Raceway diameter inner ring [inch] | 6.634 |
| C [inch] | 4.724 |
| r min Chamfer outer ring | 2 mm |
| r1 min Chamfer inner ring | 2 mm |
| Cr Radial Dynamic [lbf] | 154212 |
| C0r Radial Static [lbf] | 310224 |
| Mounting dimensions | |
| da min shaft [inch] | 6.299 |
| Da max housing [inch] | 7.874 |
| Da min housing [inch] | 7.717 |
| ra max Fillet radius [inch] | 0.079 |
| rb max Fillet radius [inch] | 0.079 |
The 30FC21120 Four-row cylindrical roller bearings mainly consist of an inner ring, an outer ring, four rows of cylindrical rollers, a cage, and a spacer. Common structures use a configuration of double outer rings (each with double raceways) and a single inner ring (with four raceways), or an interchangeable combination of inner and outer rings. Axial positioning and load distribution are achieved through the spacer.
The advantages of four-row cylindrical roller bearings are their extremely high radial load capacity, high rigidity, and the line contact between the rollers and raceways, resulting in a low coefficient of friction and allowing for high-speed operation under heavy loads. They can also be used as floating end bearings, capable of withstanding axial displacement caused by thermal expansion, and are easy to install and maintain.















