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Tapping trouble shooting chart
Use this table for any tapping problem you might run into
*Table provided by NACHI AMERICA cutting tools
 
Troubles
Factors
Countermeasures

Surface
Roughness

 

Torn or Rough
Thread
Chamfer length too short
  • Increase chamfer length
Wrong cutting angle
  • Apply proper cutting angle
Galling
  • Use thread relieved taps
  • Reduce land widths
  • Apply surface treatment such as
    steam oxide or chrome
  • Use proper cutting lubricant
    Reduce tapping speed
  • Use larger drill size
  • Obtain proper alignment
    between tap and work
Chip packing
  • Use spiral pointed or spiral fluted taps
  • Use larger drill size
Chattering on
Tapped Thread
Too free cutting
  • Avoid too narrow land width
  • Reduce amount of thread relief
Tool condition
  • Reduce cuffing angle
  • Do not grind bottom of the flute

Dimensional
Error

 

 

 

 

 

 

 

Dimensional
Error

 

 

 

 

 

 

 

 

Dimensional
Error

Oversize Pitch
Diameter
Incorrect Taps
  • Use proper GH limits
  • Use longer chamfered taps
Chip packing
  • Use spiral point or spiral fluted taps
  • Reduce number of flutes to provide extra chip room
  • Use national fine pitch, if applicable
  • Use larger drill size
  • If tapping a blind hole, allow deeper hole where
    applicable or shorten the thread length of the parts
  • Use proper lubricant
Galling
  • Apply proper surface treatment such as steam oxide
  • Use proper cutting lubricant
  • Reduce tapping speed
  • Use proper cutting angle in accordance with material being tapped
  • Use larger drill size
Operating conditions
  • Apply proper tapping speed
  • Correct alignment of tap and drill hole
  • Free cutting either tap or workpiece
  • Use proper tapping speed to avoid torn or rough thread
  • Use lead screw tapper
Tool conditions
  • Obtain proper indexing angle for the flutes at the cutting edge
  • Grind proper indexing angle and chamfer angle
  • avoid too narrow a width
  • Remove burrs from reground edge
Oversize
Internal
Diameter
Drill hole size
  • Use minimum size drill hole
  • Avoid tapered hole
  • Use proper chamfered taps
Galling
  • Galling solutions 1 through 4 above can be applied to this specific problem
Undersize
Pitch
Diameter
Incorrect tap selection
  • Use one oversize taps:
    1) Use for cutting materials such as copper alloy, aluminum alloy, and cast iron
    2) Use for cutting tubing witch will have "spring back" action after tapping
  • Apply proper chamfer angle
  • Increase cutting angle
Damaged thread
  • Use proper reversing speed to avoid damaging tapped thread the way out of the hole
Left over chips
  • Increase cutting performance to avoid any leftover chip in the hole
  • Remove leftover chip from the hole for gage checking
Undersize
Internal
Diameter
Drill hole size
  • Use maximum drill size

Tool Life

 

 

 

 

 

 

 

 

 

Tool Life

 

 

 

 

 

 

 

 

 

Tool Life

Breakage

Incorrect tap selection
  • Use high speed steel taps
  • Avoid chip packing in the flutes or the bottom of the hole
  • Use spiral pointed or spiral fluted taps or roll taps
  • Apply correct surface treatment such as steam oxide or other coating
Excessive Tapping Torque
  • Use larger drill size
  • Try to shorten thread length
  • Apply national fine pitch if applicable
  • Increase cutting angle
  • Apply a tap with more thread relief and reduced land width
  • Use spiral pointed or spiral fluted taps
Operating conditions
  • Reduce tapping speed
  • Avoid misalignment between tap and the hole and tapered hole
  • Use floating type of tapping holder
  • Use tapping holder with torque adjustment
  • Avoid hitting bottom of the hole with tap
Tool condition
  • Do not grind the bottom of the threads
  • Avoid too narrow land width
  • Do not leave sections on the reground flutes which tapping wear still remains
  • Regrind tool more frequently
Chipping Incorrect tap selection
  • Reduce cutting angle
  • Use different kind of high speed steel taps
  • Reduce hardness of taps
  • Increase chamfer length
  • Avoid chip packing in the flutes or the bottom of the hole by using spiral pointed or fluted taps
Operating conditions
  • Reduce tapping speed
  • Avoid misalignment between tap and hole
  • Avoid sudden reverse or return in blind hole tapping
  • Avoid galling
  • Use larger drill size
Wear Incorrect tap selection
  • Apply specially designed taps for tapping heat treated materials
  • Change to a type of high speed steel material containing vanadium
  • Apply special surface treatment such as nitriding or TiN
  • Increase chamfer length
Operating conditions
  • Reduce tapping speed
  • Apply proper cutting lubricants
  • Avoid work hardened hole
  • Use larger drill size
Tool condition
  • Grind proper cutting angle
  • Avoid hardness reduction from grinding process