Precision Cylindrical
Roller Bearings
NN / NNU / N Series | 25–500mm Bore | P5/P4/P2 Grade | Double-Row & Single-Row
Precision double-row and single-row cylindrical roller bearings engineered for maximum radial rigidity in machine tool main spindles, grinding spindles, and high-speed turning centers. NN and NNU double-row designs provide the industry's highest radial stiffness — the standard choice for the non-locating (floating) end of spindle bearing arrangements. Tapered bore (K suffix) variants enable precision radial clearance adjustment via a 1:12 tapered shaft journal.
Precision Cylindrical Roller Bearings for Machine Tool Spindle Radial Support
Luoyang Songju precision cylindrical roller bearings are manufactured in NN (double-row, ribbed inner ring), NNU (double-row, ribbed outer ring), and N/NU (single-row) series to ISO dimensional standards. Each bearing is produced from vacuum-degassed GCr15 (100Cr6 / 52100) bearing steel in our ISO 9001:2015 certified facility in Luoyang, China — the historic center of precision bearing manufacturing.
The NN and NNU double-row bearings are purpose-engineered for the non-locating (floating) end of machine tool spindle arrangements. Their separable ring design — where the outer ring (NN) or inner ring (NNU) can be removed from the roller-and-ring assembly — facilitates straightforward installation and removal without damaging precision-ground rolling surfaces. Line contact between cylindrical rollers and raceways delivers the highest radial load capacity and stiffness of any rolling bearing type in a given cross-section.
NN series (ribbed inner ring, smooth outer ring) allows the outer ring to float axially within the housing to accommodate thermal expansion of the shaft — essential for high-speed spindles where temperature gradients between shaft and housing can exceed 20–30°C in operation. NNU series (ribbed outer ring, smooth inner ring) provides the inverse arrangement. Tapered bore variants (K suffix, 1:12 taper) enable precision radial internal clearance adjustment by advancing the inner ring onto a tapered shaft journal — a capability unique to cylindrical roller bearings and critical for achieving optimal spindle running accuracy.
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Three Series Configurations Available
Choose the right cylindrical roller bearing configuration for your spindle's radial support requirements
NN Series
Double-row with ribs on the inner ring and a smooth outer ring. The outer ring is separable from the roller-and-inner-ring assembly. Most popular spindle configuration — outer ring floats axially in housing to accommodate thermal shaft expansion.
NNU Series
Double-row with ribs on the outer ring and a smooth inner ring. The inner ring is separable from the outer-ring-and-roller assembly. Preferred when axial displacement is desired at the shaft interface.
N / NU Series
Single-row designs in N (ribbed inner ring), NU (ribbed outer ring), and NJ (ribbed inner + single-rib outer) configurations. Compact, economical solution for spindles with moderate radial loads.
Cylindrical Roller Bearing Model Parameters
Standard model list covering NN, NNU, and N series. All models available in P5, P4, and P2 (ABEC-5/7/9) precision grades. Data per NTN precision bearing catalog specifications.
| Bearing Model | Series | d (mm) | D (mm) | B (mm) | Cr (kN) | C0r (kN) |
|---|---|---|---|---|---|---|
| NN Series — Double-Row, Ribbed Inner Ring | ||||||
| NN3006 | NN30 | 30 | 55 | 19 | 29.0 | 34.0 |
| NN3007 | NN30 | 35 | 62 | 20 | 39.3 | 50.0 |
| NN3008 | NN30 | 40 | 68 | 21 | 45.0 | 58.5 |
| NN3009 | NN30 | 45 | 75 | 23 | 54.0 | 72.0 |
| NN3010 | NN30 | 50 | 80 | 23 | 57.0 | 80.0 |
| NN3011 | NN30 | 55 | 90 | 26 | 72.0 | 100.0 |
| NN3012 | NN30 | 60 | 95 | 26 | 75.0 | 110.0 |
| NN3013 | NN30 | 65 | 100 | 26 | 76.5 | 118.0 |
| NN3014 | NN30 | 70 | 110 | 30 | 98.0 | 151.0 |
| NN3015 | NN30 | 75 | 115 | 30 | 100.0 | 156.0 |
| NN3016 | NN30 | 80 | 125 | 34 | 120.0 | 186.0 |
| NN3018 | NN30 | 90 | 140 | 37 | 143.0 | 228.0 |
| NN3020 | NN30 | 100 | 150 | 37 | 157.0 | 265.0 |
| NN3022 | NN30 | 110 | 170 | 45 | 220.0 | 370.0 |
| NN3024 | NN30 | 120 | 180 | 46 | 233.0 | 405.0 |
| NN3026 | NN30 | 130 | 200 | 52 | 284.0 | 495.0 |
| NN3028 | NN30 | 140 | 210 | 53 | 310.0 | 550.0 |
| NN3030 | NN30 | 150 | 225 | 56 | 335.0 | 615.0 |
| NN3032 | NN30 | 160 | 240 | 60 | 375.0 | 695.0 |
| NN3034 | NN30 | 170 | 260 | 67 | 450.0 | 835.0 |
| NN3036 | NN30 | 180 | 280 | 74 | 530.0 | 985.0 |
| NN3040 | NN30 | 200 | 310 | 82 | 630.0 | 1190.0 |
| NN3044 | NN30 | 220 | 340 | 90 | 750.0 | 1460.0 |
| NN3048 | NN30 | 240 | 360 | 92 | 800.0 | 1600.0 |
| NN3052 | NN30 | 260 | 400 | 104 | 990.0 | 1980.0 |
| NN3056 | NN30 | 280 | 420 | 106 | 1050.0 | 2150.0 |
| NN3060 | NN30 | 300 | 460 | 118 | 1230.0 | 2520.0 |
| NNU49 Series — Double-Row, Ribbed Outer Ring | ||||||
| NNU4920 | NNU49 | 100 | 140 | 40 | 145.0 | 285.0 |
| NNU4922 | NNU49 | 110 | 150 | 40 | 157.0 | 320.0 |
| NNU4924 | NNU49 | 120 | 165 | 45 | 196.0 | 405.0 |
| NNU4926 | NNU49 | 130 | 180 | 50 | 239.0 | 500.0 |
| NNU4928 | NNU49 | 140 | 190 | 50 | 252.0 | 540.0 |
| NNU4930 | NNU49 | 150 | 210 | 60 | 310.0 | 660.0 |
| NNU4932 | NNU49 | 160 | 220 | 60 | 330.0 | 720.0 |
| NNU4936 | NNU49 | 180 | 250 | 69 | 440.0 | 980.0 |
| NNU4940 | NNU49 | 200 | 280 | 80 | 550.0 | 1230.0 |
| NNU4944 | NNU49 | 220 | 300 | 80 | 580.0 | 1330.0 |
| NNU4948 | NNU49 | 240 | 320 | 80 | 600.0 | 1430.0 |
| NNU4952 | NNU49 | 260 | 360 | 100 | 880.0 | 2080.0 |
| NNU4956 | NNU49 | 280 | 380 | 100 | 870.0 | 2100.0 |
| NNU4960 | NNU49 | 300 | 420 | 118 | 1160.0 | 2750.0 |
| N/NU Series — Single-Row Cylindrical Roller Bearings | ||||||
| N1008 | N10 | 40 | 68 | 15 | 30.0 | 32.5 |
| NU1008 | NU10 | 40 | 68 | 15 | 30.0 | 32.5 |
| N1010 | N10 | 50 | 80 | 16 | 37.5 | 44.0 |
| NU1010 | NU10 | 50 | 80 | 16 | 37.5 | 44.0 |
| N1012 | N10 | 60 | 95 | 18 | 52.0 | 62.0 |
| N1014 | N10 | 70 | 110 | 20 | 66.0 | 82.0 |
| N1016 | N10 | 80 | 125 | 22 | 78.0 | 100.0 |
All models available in P5, P4, and P2 (ABEC-5/7/9) precision grades. Standard material: GCr15 (100Cr6/52100) bearing steel. K suffix = tapered bore (1:12 taper). W33 suffix = lubrication groove + 3 holes in outer ring. B suffix = machined brass cage (double-pronged). HS/T2 suffix = high-speed resin cage. SP = special precision for machine tools. C1NA/C2NA = lathe spindle clearance classes. NTN, NSK, SKF, and FAG interchangeable. Custom configurations available — contact engineering for complete catalog.
Why Choose Luoyang Songju Cylindrical Roller Bearings
Engineered for maximum radial rigidity and precision in the world's most demanding spindle applications
Maximum Radial Rigidity
Line contact between cylindrical rollers and precision-ground raceways delivers the highest radial stiffness of any rolling bearing type. NN/NNU double-row designs provide up to 2× the radial load capacity of equivalent single-row bearings — critical for minimizing spindle deflection under heavy cutting loads and ensuring consistent machining accuracy.
Separable Ring Design
The outer ring (NN series) or inner ring (NNU series) can be removed from the roller-and-ring assembly — simplifying installation, inspection, and replacement without damaging precision-ground rolling surfaces. A practical advantage that reduces maintenance downtime and total cost of ownership.
Thermal Expansion Accommodation
NN series (smooth outer ring) enables the outer ring to float axially within the housing — absorbing shaft thermal expansion without inducing preload variation. Essential for high-speed spindles where temperature gradients can exceed 20–30°C between shaft and housing in continuous operation.
Tapered Bore — Adjustable Clearance
K suffix (1:12 taper) variants enable precision radial internal clearance adjustment by advancing the inner ring onto a tapered shaft journal. Achieve the exact running clearance or light preload your spindle design requires — a capability not available with cylindrical bore bearings and critical for ultra-precision spindle performance.
High-Speed Optimized
Optimized roller profiles with precision-machined brass cages (B suffix) or high-speed resin cages (T2/HS suffix) and controlled internal clearances (C1NA/C2NA for lathe spindles) enable reliable operation at the elevated speeds demanded by modern CNC machining centers, grinding spindles, and high-speed turning centers.
NTN / NSK / SKF / FAG Interchangeable
Manufactured to ISO dimensional standards for NN, NNU, and N series. Direct drop-in replacement for NTN, NSK, SKF, and FAG precision cylindrical roller bearings. Same mounting dimensions, same performance — competitive pricing with shorter lead times from our ISO 9001:2015 certified Luoyang facility.
Industries & Applications for Cylindrical Roller Bearings
Precision cylindrical roller bearings deliver unmatched radial performance across the most demanding industrial applications
Machine Tool Spindles
NN series double-row bearings are the industry standard for the non-locating (floating) end of CNC lathe, milling, and grinding spindles. Paired with angular contact ball bearings at the locating end for complete spindle support with optimal thermal management.
High-Precision Grinding
Ultra-precision P2 grade NN bearings with controlled clearance enable sub-micron runout for surface, cylindrical, and internal grinding operations. Tapered bore variants allow fine clearance adjustment to optimize grinding wheel finish quality.
Rolling Mill Roll Necks
Large NN and NNU bearings (bore 200mm+) support the extreme radial loads and shock conditions of steel and aluminum rolling mill work rolls. W33 lubrication provisions and reinforced brass cages ensure reliability under continuous heavy-duty operation.
Printing & Converting Machinery
NNU series with ribbed outer ring is preferred for printing cylinders, coating rollers, and paper converting machinery. High running accuracy ensures consistent registration, uniform coating thickness, and minimal waste in high-speed web processing lines.
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