NNU 4944 SK.M.SP Bore 220 Mm, Cylindrical Roller Bearing, Double Row, Separable, With Brass Cage
The NNU 4944 SK.M.SP Ultra-precision cylindrical roller bearings are widely used in fields with stringent requirements for radial stiffness and rotational accuracy, such as: machine tool spindles (radial support 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 NNU 4944 SK.M.SP bearing is a Cylindrical roller bearing, double row, separable, with cage with an inner diameter of 220 mm , an outer diameter of 300 mm, a width of 80 mm. It typically uses SP = Super Precision grade precision tolerances and bearing steel rings, bearing steel rolling mlement. Its dynamic radial rated load is approximately 509712 N, its static radial rated load is approximately 1139882 N. It uses C1 standard radial clearance, together determine its load-bearing capacity, rotational accuracy, and applicable working conditions.
NNU 4944 SK.M.SP bearings ( 220 mm x 300 mm x 80 mm) have the advantages of Extremely high rotational accuracy and rigidity, high rotational speed and low heat generation, suitable for high-speed and high-positioning-precision applications, and are therefore widely used in the Machine tool spindles, high-speed motors, precision rolling mills, industrial robots, and aerospace equipment.
| Part Number | NNU 4944 SK.M.SP |
| Reference From | FAG NNU 4944 SK.M.SP |
| Series | NNU49..-S-K-M-SP |
| Bearing Type | Cylindrical roller bearing, double row, separable, with cage (Non-locating bearings) |
| Design Type | NNU = inner ring without ribs, ribs on inner ring |
| Dimension series | 49 (Light series) |
| Bore Type | K = Tapered (taper 1:12) |
| Cage | M = Brass cage, guided by rollers |
| Rows NO. | Double row |
| Radial internal clearance | C1 |
| Accuracy class | SP = Super Precision |
| External form | S = Lubricating groove and holes on the outer ring |
| Weight [lb] | 35.053 |
| Cr Radial Dynamic [lbf] | 114583 |
| C0r Radial static [lbf] | 256245 |
| Cr Radial rigidity [N/μm] | 5982 |
| nB Reference speed [rpm] | 2384 |
| nG Limiting speed [rpm] | 2961 |
| d φ Inside [inch] | 8.661 |
| D Φ Outside [inch] | 11.811 |
| B Width [inch] | 3.150 |
| r(min.) [inch] | 0.083 |
| s [inch] | 0.169 |
| F [inch] | 9.646 |
| ds [inch] | 0.248 |
| ns [inch] | 0.480 |
| Mounting dimensions | |
| da(h12) [inch] | 9.567 |
| Da(H12) [inch] | 10.984 |
| ra(max.) [inch] | 0.083 |
The NNU 4944 SK.M.SP Ultra-precision cylindrical roller bearings are primarily composed of high-precision inner and outer rings (made of precision-ground bearing steel), cylindrical rollers (graded to P4 or higher precision), and a cage (solid brass or outer ring guided type). Common structures include the N10 series (double-flange outer ring, no flange inner ring) and the NN30 series (double-row structure), with the rollers and raceways employing a logarithmic curve profile design.
Ultra-precision cylindrical roller bearings exhibit extremely high radial stiffness, making them suitable for precision spindles requiring heavy loads and high rigidity. They offer high limiting speeds, and optimized roller end face and flange contact 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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