(Super-Precision Angular Contact Bearing Systems)
Many CNC and grinding spindles use SKF 719xx and 70xx super-precision angular contact bearing series. These are commonly installed in matched sets with specific preload classes and arrangement configurations.
If your spindle uses SKF 719 or 70 series bearings, rebuild precision is critical.
SKF 719xx Series (Thin Section, High-Speed)
The 719xx series is a light cross-section, high-speed precision angular contact bearing commonly used in:
- High-speed VMC spindles
- Grinding spindles
- Mold & aerospace machining platforms
- Oil-air lubrication systems
Common Configurations:
- 71908, 71910, 71912, 71914, 71916, 71918, 71920
- Back-to-back (DB)
- Face-to-face (DF)
- Tandem (DT)
- Universal matched sets (UL, UM, UH preload classes)
Why 719xx Bearings Fail:
- Preload class mismatch
- Over-greasing
- Oil-air imbalance
- Contamination
- Thermal drift from incorrect assembly
These bearings are optimized for high RPM and low friction — meaning preload control must be exact.
SKF 70xx Series (Heavier Section, Higher Load Capacity)
The 70xx series is a slightly heavier cross-section angular contact bearing, often selected for increased stiffness and load capacity.
Common Sizes:
- 7008
- 7010
- 7012
- 7014
- 7016
- 7018
- 7020
These are frequently found in:
- CNC machining centers
- Toolroom mills
- Mid-range VMC platforms
- Cartridge spindle assemblies
Common Failure Causes:
- Improper preload setup
- Mismatched bearing pairs
- Contamination ingress
- Imbalance at speed
- Excess radial loading
70xx series bearings are more forgiving than 719xx, but still require precision assembly.
Understanding SKF Preload Classes
SKF super-precision bearings are available in defined preload classes such as:
- UL (Light preload)
- UM (Medium preload)
- UH (High preload)
Incorrect preload selection can cause:
- Heat rise
- Radial play
- Finish chatter
- Premature fatigue
- Thermal instability
Spindle rebuild precision is not just about size — it’s about preload accuracy.
Matched Sets & Arrangement Matters
SKF 719xx and 70xx bearings are commonly installed as:
- Duplex pairs
- Triplex sets
- Tandem arrangements
Improper orientation or mismatching destroys bearing life quickly.
During rebuild, bearing arrangement must match the spindle’s original engineering design intent.
Symptoms of 719xx / 70xx Bearing Failure
- Vibration increasing with RPM
- Heat buildup during idle
- Surface finish degradation
- Audible rumble at speed
- Measured taper runout growth
High-speed 719xx failures often show heat first.
70xx failures often show vibration and chatter first.
Our Approach to SKF Bearing-Series Rebuilds
When servicing spindles using 719xx or 70xx series bearings, we focus on:
- Confirming exact bearing designation
- Matching preload class
- Controlled preload assembly
- Balance verification
- Lubrication method validation
- Runout confirmation
- Thermal stabilization testing
The goal is to restore both stiffness and temperature stability at operating RPM.