Common CNC spindle problems

How to diagnose spindle problems

1. Listen to abnormal noise whining / buzzing = misalignment

Grinding sound = bearing damage

Chatter = cutting instability

Early detection can be done with a mechanical stethoscope or microphone.

2. Check for radial runout

Using the Percentage Table:

Mounted on the spindle taper bore

Manual rotation (no power)

Acceptable radial runout range:

ISO40 taper bore: <0.005 mm ISO30

Taper bore: <0.01 mm

If the cutter bar runs out radially > the spindle runs → the problem lies in the cutter bar or chuck

3. Check the clamping of the tool

Dirty cone hole = poor contact

Worn rivets = tool movement

HSK Shank: Check cone wear + clamping ring integrity

CAT/BT Tool Holder: Check the tie rod tension

4. Vibration analysis

Use a vibration analyzer or related application (e.g., FFT analyzer)

Focus on peaks in specific speed ranges (resonance)

Record vibrations during cutting to spot patterns

Common spindle-related CNC system alarms (take Fanuc as an example)