1 Model Information & Technical Parameters

Model：NN 3012 KTN/VQ055

Dimensions

Bore d：60 mm

Outer diameter D：95 mm

Width B：26 mm

Bore type: 1:12 tapered bore

Radial clearance: C1 minimal internal clearance

Accuracy class: SP precision grade

Structure: NN double row design, inner ring with three ribs, ribless outer ring

Outer ring flange: None

Seal: Open design, no seals

Surface coating: Uncoated

Pre-lubrication: No lubricant supplied from factory

Re-lubrication feature: No lubrication groove & oil holes on outer ring, not for on-line re-lubrication

Code Explanation

NN: Double row cylindrical roller bearing, three ribs on inner ring. Rollers are restrained axially and able to withstand slight bidirectional axial loads.

3012: Size series 30 medium cross-section double row bearing, balancing high load capacity and medium-high speed performance.

K: 1:12 tapered bore; preload and internal clearance can be adjusted axially by lock nut.

TN: Solid polyamide non-metallic roller-guided cage featuring low friction and low noise.

SP: Precision accuracy grade with strictly controlled rotational runout for precision machine tool spindles.

VQ055: Special exclusive quality specification with strict production inspection standards.

Load & Speed Data

Basic dynamic load rating Cr：73.7 kN

Basic static load rating C0r：106 kN

Permissible speed, grease lubrication：9 500 r/min

Permissible speed, oil-air lubrication：11 000 r/min

Material & Additional Properties

Material: Bearing steel

Indicative carbon footprint：2.2 kg CO₂e

Net weight：0.6 kg

eClass code：23-05-09-01

UNSPSC code：31171505

Suffix Explanation

NN: Double row cylindrical roller bearing with triple-rib inner ring. Double roller rows deliver much higher radial rigidity than single row bearings of identical outer dimensions. It can bear small bidirectional axial loads, and rollers have limited axial displacement without large floating capacity.

3012: Medium cross-section Series 30 double row bearing with high load capacity, suitable for spindle assemblies requiring superior radial stiffness.

K: 1:12 tapered bore. Axial pushing via lock nut expands inner ring radially, making continuous adjustment of clearance and preload possible during assembly.

TN: Polyamide cage, lightweight non-metallic construction with low friction coefficient for continuous medium-high speed operation under stable temperature.

SP: Precision accuracy grade. Dimensional tolerance, radial and axial runout are tighter than standard bearings to guarantee machining precision.

C1 clearance: Minimal radial internal clearance, commonly adopted in preloaded precision spindle systems to suppress high-speed vibration.

VQ055: Dedicated quality control specification covering raw material, machining and final inspection for stable product consistency.

Important reminder: This 1:12 tapered bore NN-type double row cylindrical roller bearing has no outer ring lubrication groove or oil holes. On-line continuous lubricant replenishment during machine operation is not available. It fits intermittent lubrication or one-time grease filling during assembly. Preload adjustment via lock nut must be operated gently; excessive tightening will eliminate clearance completely and cause raceway overheating damage. It withstands slight bidirectional axial loads, while heavy axial loads require matched angular contact ball bearings or thrust bearings. Open bearing without built-in seals; labyrinth seals or oil seals must be installed on housings to block coolant and dust ingress. No pre-filled grease upon delivery; lubricant should be filled during assembly. Never strike inner or outer ring directly during assembly to prevent indentations on raceways and rollers.

Alternative variants:

NN3012 TN/SPW33 (straight bore, W33 lubrication groove, support on-line re-lubrication)

NN3012 KTN/SPW33 (1:12 tapered bore, W33 lubrication groove, adjustable preload + on-line re-lubrication)

NN3012 KTN/SP (1:12 tapered bore, SP grade, without VQ055 quality standard)

NN3012 KTNHA/VQ055 (high-temperature polyamide cage for high ambient temperature)

NN3012 KTN/UP (UP ultra-precision grade for ultra-precision mirror machining spindles)

2 Structure & Operating Characteristics

NN 3012 KTN/VQ055 is a medium-size double row precision cylindrical roller bearing, SP accuracy class with C1 minimal radial clearance, TN polyamide cage, 1:12 tapered bore and non-grooved outer ring. The double-row roller layout greatly improves radial load capacity and spindle radial rigidity compared with single row bearings of equal envelope dimensions, widely used as radial support for precision machine tool spindles. The triple-rib inner ring limits roller axial movement and bears minor bidirectional axial forces.

The core advantage is adjustable preload through 1:12 tapered bore. Preload can be tuned on-site with lock nuts without tight tolerance control on shaft journals, simplifying assembly work. Without outer ring lubrication channels, it is not recommended for non-stop production requiring continuous on-line greasing; better suited for intermittent processing with periodic shutdown maintenance. Open construction supports oil-air lubrication, circulating oil lubrication and one-time grease filling. Combined C1 minimal clearance and precision manufacturing tolerances reduce rotary vibration at high speed and stabilize workpiece surface finish.

Selection guide:

NN3012 KTN/VQ055 (1:12 tapered bore, no lubrication groove, SP C1 clearance, VQ055 spec, spindles needing adjustable preload & intermittent lubrication)

NN3012 KTN/SPW33 (1:12 tapered bore with W33 groove, adjustable preload plus continuous on-line lubrication)

NN3012 TN/SPW33 (straight bore, fixed interference fit, support continuous re-lubrication)

NN3012 KTNHA/VQ055 (heat-resistant cage for high ambient temperature)

NN3012 KTN/UP (ultra-precision grade for optical and mirror finishing equipment)

Recommended matching bearing: 23412 precision double-direction thrust bearing or 7012 SP angular contact ball bearing to sustain heavy axial loads.

3 Core Performance Advantages

1. NN double roller row design delivers outstanding radial load capacity and excellent spindle rigidity, minimizing spindle deflection under cutting forces.

2. K-type 1:12 tapered bore enables on-site preload adjustment by lock nut, lowering machining requirements for shaft journals and improving assembly flexibility.

3. TN polyamide non-metallic cage ensures stable rotation and low friction, reducing operational noise under medium-high speed conditions.

4. SP precision standard together with C1 minimal radial clearance achieves tight control over rotational runout, mitigates high-speed vibration and stabilizes dimensional accuracy in finishing processes.

5. Triple-rib inner ring construction accepts slight bidirectional axial loads and simplifies spindle bearing configuration.

6. VQ055 special quality specification implements strict full-process inspection for higher product consistency; bearing steel guarantees stable contact performance of raceways and rollers.

4 Typical Application Fields

4.1 Vertical & horizontal machining center spindle units

Finishing spindles of medium-sized machining centers for intermittent production with periodic shutdown greasing

4.2 Jig grinders, CNC tool grinders and cylindrical grinders

Precision grinding machines requiring accurate spindle preload setting, strict control on rotary accuracy and vibration

4.3 Precision CNC lathes and turn-mill composite machine spindles

Medium-small batch finishing equipment without continuous automatic lubrication system

4.4 Other high-end precision intermittently operating rotary components

Precision rotating machinery demanding high radial rigidity, adjustable preload, capacity for minor bidirectional axial loads and regular maintenance

5 Assembly Specifications & Usage Guidelines

5.1 Assembly Environment & Operation Standards

SP precision bearings should be assembled in constant-temperature dust-free clean workshops. Thoroughly remove contaminants on shaft journals, housing bores and spacer contact surfaces. Preload is adjusted by axially pushing inner ring with lock nut. Operate slowly, monitor no-load temperature rise and vibration during adjustment to avoid excessive preload. No circumferential positioning requirement for outer ring without lubrication holes. After assembly, implement low-speed gradual speed-up no-load running-in. Reliable sealing must be installed on machine housings to prevent coolant and dust from reaching rolling surfaces.

5.2 Selection Guidance

On-site preload adjustment required, intermittent lubrication, no continuous on-line oil supply → NN3012 KTN/VQ055

Adjustable preload plus continuous automatic lubrication system equipped → NN3012 KTN/SPW33

No on-site preload adjustment needed, continuous re-lubrication required → NN3012 TN/SPW33

Production line with high ambient temperature and all-day continuous operation → KTNHA high-temperature cage version

Ultra-precision mirror machining requiring top-tier rotary accuracy → NN3012 KTN/UP

Important notice: No outer ring lubrication groove for this model, continuous lubricant replenishment during running is impossible. It only withstands small bidirectional axial loads; dedicated axial support bearings are mandatory under sustained heavy axial force.

5.3 Lubrication Maintenance Instruction

No lubricant pre-filled at factory. Oil-air lubrication is preferred to reach maximum permissible speed; one-time grease filling during assembly is acceptable for intermittent medium-low speed machining. Periodic shutdown for regreasing is necessary, on-line greasing cannot be realized. Monitor bearing temperature regularly and avoid prolonged overheating. Long-term insufficient lubrication will cause premature wear of rollers and cage.

5.4 Environmental Application Notes

Open structure without built-in seals; labyrinth seals or oil seals on housings are compulsory. Raceways and rollers are extremely sensitive to tiny hard particles. Contamination amplifies vibration and rapidly deteriorates machining accuracy. Frequent shock loads should be avoided to prevent indentations on rolling contact surfaces.

6 Fault Identification

Common failure modes: rising vibration during cutting, regular texture patterns on machined workpieces, sustained abnormal spindle temperature increase, periodic rotational noise, cage abrasion, roller end scuffing and raceway fatigue spalling. Typical problems for tapered bore bearings include excessive preload leading to persistent overheating, and insufficient lubrication caused by lack of regular regreasing. Shut down equipment immediately upon persistent abnormal noise or irreversible accuracy degradation. Bearings with permanent damage to raceways, rollers or cage cannot be repaired and need complete replacement.