NNU4948BK/SPW33 Bore 240 Mm, Cylindrical Roller Bearing, Double Row, Super-precision
The NNU4948BK/SPW33 Ultra-precision cylindrical roller bearings are widely used in fields with stringent requirements for radial stiffness and rotational accuracy, including: machine tool spindles (radial supports for lathe and grinding machine spindles), high-speed electric spindles, rolling mills (precision rolls), industrial robot joints, precision measuring equipment, and high-precision rotating mechanisms in aerospace.
The NNU4948BK/SPW33 bearing is a Cylindrical roller bearing, double row, super-precision with an inner diameter of 240 mm , an outer diameter of 320 mm, a width of 80 mm. It typically uses SP (ABEC 7) grade precision tolerances and GCr15SiMn rings, Carbon chromium steel rolling mlement. Its dynamic radial rated load is approximately 527147 N, its static radial rated load is approximately 1214354 N. It uses CN standard radial clearance, Open type, together determine its load-bearing capacity, rotational accuracy, and applicable working conditions.
NNU4948BK/SPW33 bearings ( 240 mm x 320 mm x 80 mm) have the advantages of Ultimate stability, ultimate precision, ultimate durability, and are therefore widely used in the Machine tool spindles, high-speed motors, precision rolling mills, industrial robots, and aerospace equipment.
| Part Number | NNU4948BK/SPW33 |
| Interchangeable | SKF NNU4948BK/SPW33 |
| Cage | Machined brass cage, prong-type, roller centred |
| Bearing Type | Cylindrical roller bearing, double row, super-precision |
| Load | radial |
| Accuracy class | SP (ABEC 7) |
| Coating | NO |
| Bearing part | Complete |
| Internal design | B = Modified internal design |
| Dimension series | 49 = ISO dimension series 49 |
| Design | NNU |
| Internal clearance | CN |
| Row NO. | Two |
| Seal | Open |
| Number of ring | outer ring(3), inner ring(0) |
| Units | Metric |
| Manufacturer Part Code | NNU 4948 BK/SPW33 |
| Series | NNU 49 series (NNU 49.. BK/SPW33) |
| Lubrication | NO |
| Relubrication feature | W33 = Annular groove and three lubrication holes in the outer ring |
| Loose flange | NO |
| Weight [lb] | 39.0214 |
| Cr Radial Dynamic [lbf] | 118502 |
| C0r Radial Static [lbf] | 272986 |
| Pu Fatigue load limit [lbf] | 26469 |
| nB Speed ratings (grease) [rpm] | 2110 |
| nG Speed ratings (oil) [rpm] | 2506 |
| d φ Inside [inch] | 9.4488 |
| D Φ Outside [inch] | 12.5984 |
| B Thickness [inch] | 3.1496 |
| F [inch] | 10.433 |
| b [inch] | 0.4370 |
| K [inch] | 0.1181 |
| r1,2 min Chamfer [inch] | 0.0827 |
| r3,4 min Chamfer [inch] | 0.0433 |
| D1 [inch] | 11.5039 |
| dn Oil nozzle [inch] | 10.5118 |
| s max. Permissible axial displacement [inch] | 0.1457 |
| ra max Radius of fillet [inch] | 0.0787 |
| da min [inch] | 9.8819 |
| Da max [inch] | 12.165 |
| da max [inch] | 10.315 |
| Gref Reference grease quantity | 171 |
| Static radial stiffness [N/µm] | 6340 |
The NNU4948BK/SPW33 Ultra-precision cylindrical roller bearings are primarily composed of high-precision inner and outer rings (bearing steel precision ground to P4 grade or higher), cylindrical rollers (high-graded, often logarithmically modified), and a cage (solid brass or outer ring guided type). Common structures are the N10 series (single row) and NN30 series (double row), with separable inner and outer rings for easy installation.
Ultra-precision cylindrical roller bearings offer extremely high radial stiffness and load-carrying capacity, making them suitable for precision spindles requiring heavy loads and high rigidity. They feature high limiting speeds, optimized roller end face and flange contact to reduce friction and heat generation. Precision grades can reach P4 to P2, providing smooth rotation and low vibration. They can be used as floating end bearings to compensate for thermal expansion and maintain high positioning accuracy.
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