Think & Tinker, Ltd.
CNC router bits and carbide cutting tools with tutorials and technical guides

Milling Cutter Troubleshooting Chart

The following table lists some of the common problems encountered in machining operations. While it can be very helpful in indentifying the source of many problems, nothing replaces running a "sweet-spot test" for rapidly determining the optimum combination of machining parameters.
Problem Cause Solution
Chipping
  • Feed rate too high
  • Up milling (conventional)
  • Cutting edge too sharp
  • Chattering
  • Loose tool
  • Workpiece rigidity
  • Tool rigidity
  • Low cutting speed
  • Loose toolholder
  • Reduce feed rate
  • Change to down milling (climb)
  • Hone cutting edge or allow break-in
  • Reduce RPM
  • Remove, clean, and retighten
  • Tighten workpiece holding method
  • Shorten LOC, place shank further up holder
  • Increase RPM
  • Remove from spindle, clean and replace
Wear
  • High cutting speed
  • Low feed rate
  • Up milling (conventional)
  • Hard material
  • Poor chip evacuation
  • Improper cutter helix
  • Reduce RPM
  • Increase feed rate
  • Change to down milling (climb)
  • Use coated tool
  • Reposition coolant lines, use air blasting
  • Change to recommended helix angle
Breakage
  • Excessive spindle TIR
  • Feed rate too high
  • Depth of cut too large
  • Poor tool rigidity
  • Tool wear
  • Poor chip evacuation
  • Reduce feed rate
  • Reduce depth of cut
  • Shorten LOC, place shank further up holder
  • Replace/regrind sooner
  • Use air blasting
Chattering
  • Speed and feed too high
  • Poor toolholder rigidity
  • Poor spindle rigidity
  • Workpiece rigidity
  • Relief angle too high
  • Depth of cut too large
  • Poor tool rigidity
  • Reduce feed rate
  • Replace with shorter/more rigid holder
  • Use larger spindle or different machine tool
  • Tighten workpiece holding method
  • Regrind with smaller relief angle
  • Reduce depth of cut
  • Shorten LOC, place shank further up holder
Short Life
  • Non-optimum combination of feed and speed
  • Cutter/workpiece friction
  • Hard material
  • Poor material condition
  • Improper cutter angle
  • Use coated tool
  • Use coated tool
  • Use coated tool, clean material surface
  • Regrind with proper primary relief angle
Chip Packing
  • Feed rate too high
  • Low cutting speed
  • Insufficient chip room
  • Reduce feed rate or increase speed
  • Increase RPM or reduce feed rate
  • Use tool with less flutes, increase helix
Poor Surface
Finish
  • Feed rate too high
  • Low cutting speed
  • Tool wear
  • Edge build up
  • Depth of cut too large
  • Chip welding
  • Reduce feed rate
  • Increase RPM
  • Replace or regrind tool
  • Increase RPM, switch to higher helix tool
  • Reduce depth of cut
  • Increase volume of coolant
Burring or
Workpiece
Chipping
  • Excessive spindle TIR
  • Tool wear
  • Improper helix angle
  • Feed rate too high
  • Depth of cut too large
  • Replace or regrind tool
  • Change to recommended helix angle
  • Reduce feed rate
  • Reduce depth of cut
Workpiece
Inaccuracy
  • Loose/worn toolholder
  • Poor toolholder rigidity
  • Poor spindle rigidity
  • Insufficient number of flutes
  • Tool deflection
  • Repair or replace
  • Replace with shorter/more rigid toolholder
  • Use larger spindle or different machine tool
  • Use tool with higher flute quantity
  • Shorten LOC, place shank further up holder