Spindle Make: Perske
Model: KRSR35-7-2-SM
Tool Interface: HSK25R
Serial Number: 01414118
Condition at Arrival: Locked Up
The Situation
This Perske KRSR35-7-2-SM HSK25R spindle was brought in completely locked up. The unit could not rotate and required immediate disassembly to determine the cause of failure.
Full teardown confirmed catastrophic rear bearing failure as the root issue.
Failure Analysis
🔹 Catastrophic Rear Bearing Failure
The rear bearing had completely failed, resulting in spindle seizure. Evidence showed severe internal damage consistent with high-speed bearing collapse.
Rear bearing failure in high-speed spindles can result from:
- Lubrication breakdown
- Contamination
- Overheating
- Imbalance
- Extended runtime beyond service interval
Once the rear bearing failed, rotational movement was no longer possible.
🔹 Front Bearings Still Intact
Interestingly, the front bearing set had not yet failed.
This is important because:
- The damage had not fully propagated through the spindle assembly
- The spindle was repairable rather than requiring complete structural replacement
Early intervention prevented further escalation.
🔹 Rear Shaft Journal Damage
The catastrophic bearing event caused damage to the rear bearing journal on the shaft.
However, after inspection and measurement:
- The journal was recoverable
- Precision corrective machining restored proper geometry
- Structural integrity was preserved
Had the journal damage been deeper, shaft replacement would have been required.
Rebuild Process
Given the failure severity, a full rebuild was performed.
✔ Complete Disassembly
All components were removed for inspection and evaluation.
✔ Multi-Stage Cleaning
Each component was cleaned multiple times to remove debris from the bearing failure event.
Bearing fragmentation can contaminate:
- Bearing seats
- Housing bores
- Rotor surfaces
Thorough cleaning is critical after catastrophic events.
✔ Bearing Replacement
New sealed ABEC 7 precision deep groove bearings were installed:
- R203XSSKCA7P58LRD2U
- R-105SSKEA7P58LZ029
Sealed bearings provide improved protection against contamination and lubricant loss compared to open designs.
ABEC 7 precision class ensures:
- High-speed stability
- Tight radial tolerances
- Reduced vibration
- Improved surface finish consistency
✔ Dynamic Balancing
All rotating components were dynamically balanced:
- Prior to final assembly
- After complete assembly
Balancing is essential following a catastrophic bearing event to restore high-RPM stability.
✔ Clean Room Assembly
Final preparation and assembly were completed in our Class 10,000 clean room environment to prevent contamination during reassembly.
Testing & Certification
After rebuild:
- Spindle was run and thermally stabilized
- Break-in procedure completed
- Operational testing performed
- Performance certified
Once certification was complete, the spindle was packaged and prepared for pickup.
Key Lessons
1️⃣ Rear Bearings Often Fail First
In many spindle designs, rear bearings experience different load dynamics and can fail before front sets.
2️⃣ Early Lock-Up Can Prevent Escalation
Although severe, the failure had not yet compromised the front bearings or housing.
3️⃣ Journal Recovery Saves Significant Cost
Precision corrective machining preserved the shaft, preventing a more expensive rebuild scope.
4️⃣ Clean Assembly Is Critical After Bearing Collapse
Metal debris from failed bearings must be completely removed to prevent secondary failure.
Final Takeaway
This Perske KRSR35-7-2-SM spindle experienced catastrophic rear bearing failure that caused full lock-up. However, timely intervention and shaft journal recovery allowed the spindle to be fully rebuilt and certified without requiring structural replacement.
Addressing bearing instability early can prevent escalation into shaft or housing destruction.