SKF
Super-Precision Cylindrical Roller Bearings
SKF super-precision cylindrical roller bearings, typically in NN, NNU, and N series, are designed for radial support in machine tool spindles where high load capacity, extreme radial stiffness, and adjustable clearance are required. They are manufactured to SP, P4, and P2 tolerances and often used as the non-locating rear bearing in a spindle assembly or as the main radial bearing in grinding spindles. Their separable inner ring and roller/cage assembly facilitate mounting and allow radial clearance or preload adjustment via the tapered bore. Precision cage designs guide the rollers reliably at high speeds, and SKF Explorer quality ensures sustained accuracy and fatigue life. These bearings are frequently paired with super-precision angular contact ball bearings to form a complete spindle support system with high axial and radial precision.
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Adjustable Radial Clearance
Tapered bore allows fine preload or clearance setting.
High Radial Stiffness
Double row designs resist cutting forces and improve workpiece roundness.
Separable Inner Ring
Eases fitting on tapered shafts and allows spindle shaft regrinding.
SP, P4, P2 Tolerances
Maintain micron-level runout under heavy loads.
SKF Explorer Performance
Superior fatigue life and wear resistance.
High-Speed Compatibility
Suitable for grinding spindles and boring heads with oil-air lubrication.
Mounting Super-Precision Cylindrical Roller Bearings via Tapered Bore
The bearing is driven up its tapered shaft seat using a hydraulic nut, causing radial expansion of the inner ring and reducing internal clearance. SKF provides displacement values and radial clearance reduction gauges to achieve the precise preload or clearance required for the application.
Pairing with Angular Contact Bearings in Spindle Design
The front of a machining spindle uses angular contact bearings to handle combined loads; the rear uses a double row cylindrical roller bearing (like NNU 4920) to provide pure radial support with axial float. This pairing offers optimal stiffness and thermal stability across the spindle's speed range.