NNU Series
Double-Row Cylindrical Roller Bearings
100–500mm Bore | Ribbed Outer Ring | Separable Inner Ring | P5/P4/P2 Grade
The NNU series features ribs on the outer ring and a smooth inner ring — the structural inverse of the NN series. This design is optimized for applications where axial displacement is preferred at the shaft interface or where the outer ring is the rotating element. The separable inner ring facilitates mounting on stationary shafts.
Optimized for Outer Ring Rotation and Stationary Shaft Applications
Luoyang Songju NNU series double-row cylindrical roller bearings feature ribs on the outer ring to guide the two rows of cylindrical rollers, with a smooth inner ring that is separable from the outer-ring-and-roller assembly. This inverse configuration (compared to NN series) makes NNU bearings ideal for applications where the outer ring rotates — such as printing press cylinders, coating rollers, and paper converting machinery — or where axial displacement is preferred at the shaft interface.
The NNU49 dimensional series offers a thinner cross-section than the NN30 series at comparable bore sizes, resulting in lower weight and reduced centrifugal forces at high rotational speeds. This makes NNU bearings particularly suitable for applications where minimizing rotating mass is important — such as high-speed printing cylinders and lightweight roller assemblies in web processing lines.
Standard models are available in P5, P4, and P2 precision grades from GCr15 bearing steel with machined brass cages. The separable inner ring simplifies installation on stationary shafts — the outer ring and roller assembly can be mounted in the housing first, then the inner ring slid onto the shaft. W33 suffix variants include a lubrication groove and three oil holes in the outer ring for convenient relubrication access.
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NNU Series — Double-Row Cylindrical Roller Bearing Model Parameters
Complete NNU49 series model list per NTN precision bearing catalog. All models available in P5, P4, and P2 precision grades.
| Bearing Model | d (mm) | D (mm) | B (mm) | Cr (kN) | C0r (kN) |
|---|---|---|---|---|---|
| NNU4920 | 100 | 140 | 40 | 145.0 | 285.0 |
| NNU4922 | 110 | 150 | 40 | 157.0 | 320.0 |
| NNU4924 | 120 | 165 | 45 | 196.0 | 405.0 |
| NNU4926 | 130 | 180 | 50 | 239.0 | 500.0 |
| NNU4928 | 140 | 190 | 50 | 252.0 | 540.0 |
| NNU4930 | 150 | 210 | 60 | 310.0 | 660.0 |
| NNU4932 | 160 | 220 | 60 | 330.0 | 720.0 |
| NNU4936 | 180 | 250 | 69 | 440.0 | 980.0 |
| NNU4940 | 200 | 280 | 80 | 550.0 | 1230.0 |
| NNU4944 | 220 | 300 | 80 | 580.0 | 1330.0 |
| NNU4948 | 240 | 320 | 80 | 600.0 | 1430.0 |
| NNU4952 | 260 | 360 | 100 | 880.0 | 2080.0 |
| NNU4956 | 280 | 380 | 100 | 870.0 | 2100.0 |
| NNU4960 | 300 | 420 | 118 | 1160.0 | 2750.0 |
All models available in P5, P4, and P2 (ABEC-5/7/9) precision grades. Standard material: GCr15 (100Cr6/52100) bearing steel. NNU49 dimensional series with thinner cross-section than NN30. W33 suffix = lubrication groove + 3 holes in outer ring. B suffix = machined brass cage. NTN, NSK, SKF, FAG interchangeable. Contact engineering for non-standard sizes.
Why Choose Luoyang Songju NNU Series Cylindrical Roller Bearings
Ribbed outer ring design — optimized for outer ring rotation and stationary shaft mounting
Optimized for Outer Ring Rotation
The integral ribbed outer ring provides the most stable reference surface when the outer ring is the rotating element. Ideal for printing cylinders, coating rollers, and web processing machinery where the bearing outer ring rotates with the drum or cylinder at high speed.
Thinner Cross-Section — Lower Rotating Mass
The NNU49 dimensional series features a thinner cross-section than comparable NN30 bearings at the same bore size. Reduced rotating mass means lower centrifugal forces, lower power consumption, and the ability to achieve higher rotational speeds in outer-ring-rotating applications.
Separable Inner Ring
The smooth inner ring can be removed from the outer-ring-and-roller assembly — simplifying installation on stationary shafts. Mount the outer ring assembly in the housing first, then slide the inner ring onto the shaft for a straightforward assembly process.
W33 Lubrication Provision
Standard W33 suffix adds a circumferential lubrication groove and three equally spaced oil holes in the outer ring — enabling convenient relubrication without disassembly. Compatible with grease, oil-mist, and circulating oil lubrication systems for flexible integration into existing machine designs.
Machined Brass Cage — Proven Reliability
Double-pronged machined brass cages (B suffix) provide superior roller guidance at high speeds and under fluctuating loads compared to pressed steel or polymer alternatives. The proven cage design ensures decades of reliable operation in demanding industrial environments.
NTN / NSK / SKF Interchangeable
Manufactured to ISO dimensional standards for NNU49 series. Direct drop-in replacement for NTN NNU49, NSK NNU49, and SKF NNU49 series double-row cylindrical roller bearings. Same dimensions, same performance — competitive pricing and faster delivery.
Industries & Applications for NNU Series Cylindrical Roller Bearings
NNU Series cylindrical roller bearings are trusted across precision industries worldwide for their unmatched radial performance.
Printing Press Cylinders
NNU series is the preferred bearing for high-speed offset and rotogravure printing press cylinders. The ribbed outer ring rotates with the cylinder at production speeds up to 60,000 impressions per hour — maintaining precise registration through consistent running accuracy.
Paper & Converting Machinery
Coating rollers, calender stacks, slitter-rewinders, and corrugating rolls in paper mills and converting lines. NNU bearings handle the combined radial and moment loads of web tension while the separable inner ring enables quick roller changes during grade changeovers.
Rolling Mill Backup Rolls
Large NNU bearings support the extreme loads of steel and aluminum cold-rolling mills. The ribbed outer ring design provides stable roller guidance under the shock loading and vibration conditions characteristic of metal rolling processes.
Large Electric Motors & Generators
NNU bearings with W33 lubrication provisions support the rotor shafts of large industrial motors, generators, and alternators. The separable inner ring simplifies rotor installation and removal during equipment overhauls and rewinds.
Need NNU Series Double-Row Cylindrical Roller Bearings?
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