CARBIDE TIPPED COUNTERBORES
TECHNICAL INFORMATION
COUNTERBORE BASICS
  • The counterbore is used to enlarge a preformed hole when a flat bottom is required or to spotface when a machine finish is required
  • The counterbore is an end cutting tool which may utilize a pilot to align the enlarged hole being machined with the preformed hole
  • The three flute counterbore tends to reduce chatter & improves finish
  • Coatings are especially effective (see "Coating Selector")
COUNTERBORE SPECIFICATIONS & TOLERANCES
  • Geometry and carbide grade appropriate for material being machined
  • Carbide tips brazed to tough hardened alloy steel body, except aircraft counterbores which are not hardened
  • Precision ground cutting edges
  • USCTI
  • "Taper Shank No', refers to American Standard taper series (formerly Morse taper series) per ASME/ANSI B5.10
  • Steel cutting counterbores have secondary end relief on carbide for increased cutting edge strength
  • Tool diameter tolerance: plus .001", minus .000"
  • Shank diameter tolerance: plus .0000", minus .0005"
COUNTERBORE PROBLEM SOLVING GUIDE
COUNTERBORING PROBLEMS POSSIBLE CAUSES POSSIBLE SOLUTIONS
1. ROUGH FINISH Dull cutting edge Resharpen to original tool geometry
Wrong feeds & speeds Increase speed - also try reduced feed
2. EXCESSIVE CUTTING
EDGE WEAR 		Wrong feeds & speeds Increase feed (should always be over .001" per tooth) - especially when
machining ductile or free machining materials. Also try reduced speed
Rough cutting edge Lightly hone cutting edge with fine grit diamond hone
Insufficient coolant Increase coolant flow - review type of coolant
3. CHIPPED CUTTING EDGE Poor chip removal Use tool with larger flute space - larger diameter or fewer flutes
Recutting work hardened chips Increase coolant flow
Vibration Increase rigidity of set-up, especially worn tool holders
Incorrect carbide grade Change to tougher carbide grade
4. CHATTER MARKS Insufficient machine horsepower Use tool with fewer flutes as correct feeds & speeds must be maintained
Vibration Consider climb milling
Use larger diameter cutter
Resharpen tool with more clearance
5. GLAZED FINISH Feed too light Increase feed
Dull cutting edge Resharpen tool to original geometry
Insufficient clearance Resharpen tool with more clearance
6. POOR TOOL LIFE Excessive cratering Increase speed or decrease feed
Change to harder grade of carbide
Abrasive material Decrease speed and increase feed
Increase coolant flow
Hard materials Reduce speed - rigidity very important
Insufficient chip room Use larger diameter tool
Delayed resharpening Prompt resharpening to original geometry will increase tool life
Thermal cracked carbide Maintain adequate coolant flow at all times