NN Series
Double-Row Cylindrical Roller Bearings
25–500mm Bore | Ribbed Inner Ring | Separable Outer Ring | P5/P4/P2 Grade
The NN series is the industry-standard double-row cylindrical roller bearing for machine tool main spindles. Featuring ribs on the inner ring and a smooth outer ring, the NN design allows the outer ring to float axially within the housing — perfectly accommodating thermal expansion of the shaft during high-speed operation. The separable outer ring facilitates easy installation and maintenance.
The Industry Standard for Machine Tool Spindle Radial Support
Luoyang Songju NN series double-row cylindrical roller bearings are the most widely specified bearing type for the non-locating (floating) end of machine tool spindle arrangements. The ribs on the inner ring guide the two rows of cylindrical rollers, while the smooth outer ring can be removed from the roller-and-inner-ring assembly — making installation, inspection, and replacement straightforward without risk of damaging precision-ground rolling surfaces.
The key advantage of the NN series in spindle applications is its ability to accommodate thermal expansion. As the spindle shaft heats up during operation (temperature gradients of 20–30°C are common in high-speed spindles), the outer ring slides axially within the housing bore — preventing the buildup of destructive axial preload that would otherwise cause bearing seizure or catastrophic spindle failure.
Both cylindrical bore (standard) and tapered bore (K suffix, 1:12 taper) variants are available. The tapered bore enables precision radial internal clearance adjustment by advancing the inner ring onto a tapered shaft journal — a critical capability for achieving optimal spindle running accuracy. Standard NN30 dimensional series covers bore sizes from 25mm to 500mm. In a complete spindle arrangement, NN bearings handle radial loads at the floating end while angular contact ball bearings manage axial loads and provide axial location at the opposite end.
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NN Series — Double-Row Cylindrical Roller Bearing Model Parameters
Complete NN30 series model list per NTN precision bearing catalog. All models available in P5, P4, and P2 (ABEC-5/7/9) precision grades.
| Bearing Model | d (mm) | D (mm) | B (mm) | Cr (kN) | C0r (kN) |
|---|---|---|---|---|---|
| NN3006 | 30 | 55 | 19 | 29.0 | 34.0 |
| NN3007 | 35 | 62 | 20 | 39.3 | 50.0 |
| NN3008 | 40 | 68 | 21 | 45.0 | 58.5 |
| NN3009 | 45 | 75 | 23 | 54.0 | 72.0 |
| NN3010 | 50 | 80 | 23 | 57.0 | 80.0 |
| NN3011 | 55 | 90 | 26 | 72.0 | 100.0 |
| NN3012 | 60 | 95 | 26 | 75.0 | 110.0 |
| NN3013 | 65 | 100 | 26 | 76.5 | 118.0 |
| NN3014 | 70 | 110 | 30 | 98.0 | 151.0 |
| NN3015 | 75 | 115 | 30 | 100.0 | 156.0 |
| NN3016 | 80 | 125 | 34 | 120.0 | 186.0 |
| NN3018 | 90 | 140 | 37 | 143.0 | 228.0 |
| NN3020 | 100 | 150 | 37 | 157.0 | 265.0 |
| NN3022 | 110 | 170 | 45 | 220.0 | 370.0 |
| NN3024 | 120 | 180 | 46 | 233.0 | 405.0 |
| NN3026 | 130 | 200 | 52 | 284.0 | 495.0 |
| NN3028 | 140 | 210 | 53 | 310.0 | 550.0 |
| NN3030 | 150 | 225 | 56 | 335.0 | 615.0 |
| NN3032 | 160 | 240 | 60 | 375.0 | 695.0 |
| NN3034 | 170 | 260 | 67 | 450.0 | 835.0 |
| NN3036 | 180 | 280 | 74 | 530.0 | 985.0 |
| NN3040 | 200 | 310 | 82 | 630.0 | 1190.0 |
| NN3044 | 220 | 340 | 90 | 750.0 | 1460.0 |
| NN3048 | 240 | 360 | 92 | 800.0 | 1600.0 |
| NN3052 | 260 | 400 | 104 | 990.0 | 1980.0 |
| NN3056 | 280 | 420 | 106 | 1050.0 | 2150.0 |
| NN3060 | 300 | 460 | 118 | 1230.0 | 2520.0 |
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). T2/HS suffix = high-speed resin cage. C1NA/C2NA = lathe spindle internal clearance classes. SP = special precision. NTN, NSK, SKF, FAG interchangeable. Contact engineering for non-standard sizes and custom configurations.
Why Choose Luoyang Songju NN Series Cylindrical Roller Bearings
The spindle industry's preferred radial bearing — double-row design with ribbed inner ring for maximum radial stiffness and thermal stability
Maximum Radial Rigidity
Two rows of cylindrical rollers in line contact with raceways deliver the highest radial stiffness of any rolling bearing type in a given cross-section. The NN30 dimensional series is optimized for spindle applications — providing up to 2× the radial load capacity of equivalent single-row cylindrical roller bearings.
Thermal Expansion Compensation
The smooth outer ring floats axially within the housing bore, absorbing shaft thermal expansion without inducing preload variation. This is the defining advantage of NN series bearings in high-speed spindles — where temperature gradients exceeding 20°C between shaft and housing are routine in production machining environments.
Separable Outer Ring — Easy Handling
The outer ring can be removed from the roller-and-inner-ring assembly, allowing each component to be installed and removed independently. This simplifies spindle assembly, bearing inspection, and replacement — reducing maintenance downtime and protecting precision-ground surfaces from handling damage.
Tapered Bore Clearance Adjustment
K suffix (1:12 taper) variants enable fine adjustment of radial internal clearance by advancing the inner ring onto a tapered shaft journal. Achieve the exact running clearance — from slight positive clearance for high-speed applications to light preload for maximum stiffness — a capability unique to cylindrical roller bearings.
High-Speed Optimized Internals
Optimized logarithmic roller profiles minimize edge stress at high speeds. High-speed resin cage variants (T2/HS suffix) reduce centrifugal forces and enable higher limiting speeds. Controlled internal clearance classes (C1NA, C2NA) are specifically designed for lathe spindle applications.
NTN / NSK / SKF / FAG Interchangeable
Manufactured to ISO dimensional standards. Direct drop-in replacement for NTN NN30, NSK NN30, SKF NN30, and FAG NN30 series double-row cylindrical roller bearings. Same mounting dimensions, same performance specifications — competitive pricing with shorter lead times.
Industries & Applications for NN Series Cylindrical Roller Bearings
NN Series cylindrical roller bearings are trusted across precision industries worldwide for their unmatched radial performance.
CNC Lathe & Turning Center Spindles
NN series bearings are the de facto standard for the floating end of CNC lathe main spindles. The outer ring floats in the housing to accommodate thermal growth while the angular contact bearings at the opposite end provide axial location and thrust capacity — together forming the classic spindle bearing arrangement.
Milling & Machining Center Spindles
High-speed milling spindles demand NN bearings with controlled clearance and high-speed resin cages (T2 suffix). The separable outer ring design allows the bearing to be serviced without complete spindle disassembly — reducing machine downtime in production environments.
Grinding Spindles
Ultra-precision P2 grade NN bearings with tapered bore (K suffix) and C1NA clearance enable the sub-micron radial runout required for surface, cylindrical, and internal grinding operations. Fine clearance adjustment via the tapered bore optimizes grinding accuracy and surface finish.
Heavy-Duty Industrial Machinery
Large NN bearings (bore 200mm+) support the main shafts of electric motors, generators, gearboxes, and industrial pumps. High radial load capacity and separable design reduce total cost of ownership through extended service intervals and simplified maintenance.
Need NN Series Double-Row Cylindrical Roller Bearings?
Tell us your bore size, precision grade (P5/P4/P2), bore type (cylindrical/tapered K), cage preference, clearance class, and quantity. Our engineers will respond within 24 hours with a competitive quotation and technical documentation.