TL;DR
Spindle runout causes chatter marks and oversize cut dimensions. Measure runout with a dial indicator, check tool holder seating, and inspect spindle bearings for wear.
What you might see
- chatter marks on routed surfaces
- cut dimensions exceeding tolerance
- audible vibration at spindle speed
- tool breaking more frequently than normal
Likely causes
Contaminated or damaged tool holder taper preventing full seating
Worn spindle bearings introducing radial play
Unbalanced cutting tool from missing carbide insert or chip
Spindle collet worn or dirty, clamping tool off-center
Required tools
- Dial test indicator with magnetic base
- Test arbor
- Lint-free cleaning cloths
- LOTO kit
Safety first
- Lock out the machine before touching the spindle or tooling. Never measure runout on a rotating spindle.
- Wood routing creates fine dust. Use dust extraction and a respirator during any work near the spindle area.
- Sharp cutting edges on tooling. Use cut-resistant gloves when handling router bits.
Procedure
- 1
Stop the spindle and lock out the machine. Do not inspect a rotating spindle.
Warning: CNC router spindles rotate at high speed. Lock out the machine and wait for full spindle stop before touching any tooling. - 2
Remove the tool and clean the spindle taper and collet with a lint-free cloth. Inspect for chips, nicks, or contamination.
- 3
Mount a dial test indicator on the spindle nose and measure runout with the collet installed but no tool. Rotate the spindle slowly by hand.[1]
- 4
Runout above 0.01 mm at the collet nose indicates a worn collet, contaminated taper, or bearing wear.
- 5
Install a test arbor and measure runout again at 100 mm from the collet. Higher reading at 100 mm than at the nose points to spindle bearing looseness.[1]
- 6
If the collet is worn or the taper is damaged, replace the collet and re-measure before concluding the spindle bearings are the issue.
- 7
If bearing-related runout is confirmed, contact an SCM service technician for spindle bearing replacement or spindle exchange.
Sources
SCM SCM Morbidelli M / X CNC Router (Wood / Furniture) general technical documentation, SCM
CNC router spindle runout measurement and tooling maintenance, general CNC machining practice (general)
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