Twist Drill Troubleshooting Guide  

Hole Problems: Drill Problems:

Hole Problems

Problem Causes Solutions
Hole expansion Run out of drill when attached to the machine
Loose hold
Check holder and/or select another one
Check run out after fixing to the chuck
Non-symmetric point angle
Different lip height
Run out of chisel edge
Regrind correctly
Check preciseness after reground
Problem Causes Solutions
Irregular hole size Non-symmetric point angle
Large lip height
Run out of chisel edge
Margin wear is large
Regrind correctly
Check precision after regrind
Large run out after attached to the machine
Loose hold
Low work holding rigidity
Check holder and select another one
Check run out after fixing to the chuck
Feed rate to high Decrease feed rate
Not enough lubrication Use drill with an oil hole
Problem Causes Solutions
Low position accuracy

Low position accuracy
Large run out when attached to the machine
Large spindle run out
Check holder and/or select another one
Check run out after fixing to the chuck
Run out when cutting material Select more rigid tool and machine
Increase work clamping rigidity
Select a low cutting resistance thinning
Use centering
Work piece should be horizontal
Use a drill bush
Low alignment accuracy (for lathing) Check alignment
Problem Causes Solutions
Hole perpendicularity

Hole perpendicularity
Excessive tool wear Regrind
Low position accuracy Increase position accuracy
Non-symmetric point angle
Large lip height
Run out of chisel edge
Regrind correctly
Check precision after regrinding
Not enough drill rigidity Increase drill rigidity
Drilling surface is not horizontal
Poor alignment (for lathing)
Work piece must be horizontal
Make a center hole. Check alignment
Problem Causes Solutions
Bad cylindrical accuracy
Non-symmetric point angle
Large lip height
Run out of chisel edge
Regrind correctly
Check precision after regrinding
Large run out after attached to machine
Loose hold
Low work holding rigidity
Check hole and/or select another one
Check run out after fixing to the chuck
Relief angle is too large Regrind correctly
Low drill rigidity Use carbide drill or larger web drills
Problem Causes Solutions
Poor surface finish Poor regrinding Take off all the wear
Not suitable coolant for the material
Not enough coolant
Change supply method; increase volume
Select higher coolant quality
Large run out after attached to machine
Loose hold
Check holder and/or select another one
Check run out after fixing to the chuck
Feed rate is too high Reduce feed rate
Excessive tool wear
Build up on margin is too large
Regrind correctly
Select a coated tool
Chip packing Select suitable drill (wide flute, high helix oil hole drill). Change cutting conditions (feed rate or adopt step drilling)
Problem Causes Solutions
Bad cylindrical shape
Bad cylindrical shape
Non-symmetric point angle
Large lip height
Run out of chisel edge
Large margin wear
Regrind correctly
Check precision after regrinding
Feed rate is too low Increase the feed rate

Drill Problems

Problem Causes Solutions
Drill breakage

Drill breakage
In accurate machine
Work material deformation
Increase the rigidity of machine, drill and work clamping
Relief angle is too small Regrind correctly
Feed rate is too high Decrease the feed rate
Excessive tool wear Regrind
Chip packing Select suitable drill (wide flute, high helix oil hole drill). Change cutting conditions (feed rate or adopt step drilling).
Difficulty entering the material Select high rigid tool & rigid machine
Increase work clamping rigidity
Select a low cutting resistance thinning
Use centering
Work piece should be horizontal
Use bush drill
Problem Causes Solutions
Chipping of corner edge
Chipping of corner edge
In appropriate tool material Choose suitable tool material
Uneven hardness distribution on the work material Iso static treatment
Change tool, material & cutting conditions, machining method (EDM)
Cutting or feed speed is too high Reduce cutting speed or feed
Not enough coolant Change lubrication method
Problem Causes Solutions
Chipping of cutting edge
Chipping of corner edge
Large run out after attached to machine
Loose hold
Check holder and/or select another one
Check run out after fixing to the chuck
Relief angle is too small Regrind correctly
Tool material is not suitable Choose suitable tool material
Cutting speed or feed is too high Reduce cutting speed or feed
Problem Causes Solutions
Abnormal wear on corner part
Abnormal wear on corner part
Tool late regrinding Regrind after a shorter time of use
Bad alignment (for lathe turning) Check/adjust the alignment
Cutting speed too high Decrease the cutting speed
Point dimensions are not suitable Select correct point dimensions
Tool materials not suitable Choose suitable tool material
Coolant is not suitable Change coolant
Problem Causes Solutions
Large wear and chipping, crushing of the chisel edge Feed rate is too large Decrease feed rate
Point dimensions are not suitable Select correct point dimensions
Tool materials is not suitable Choose suitable tool material
Relief angle is too small Increase relief angle
Problem Causes Solutions
Chipping of margin Bush diameter is too small
Chip packing between drill & bush
Select correct bush diameter or select drill with chip breakers
Problem Causes Solutions
Margin built-up High heat generation due to large wear on the cutting edge Regrind
Lubrication is insufficient Change lubrication method
Coolant is not suitable Change coolant
Bad chip ejection
Ductile material
Change drill or the cutting conditions
Problem Causes Solutions
Tang breakage
Tang breakage
Shank slippage due to some kind of defect Take off the defect by honing the surface
Defect of the inner surface of Morse taper holder Change holder or correct the surface of Morse taper holder
Low accuracy of regrinding Regrind correctly
Problem Causes Solutions
Noise of chattering Relief angle is too big Grind a smaller relief angle
Low rigidity of the tool Use drill with high rigidity
Problem Causes Solutions
Chip rolled around the drill Low extended and curly chips
Chips are stubbed in the flute
Change drill and cutting conditions
Problem Causes Solutions
One side wear Large run out after attached to machine Check holder and/or select another one
Check run out after fixing to the chuck
Bad alignment (for lathe turning) Check/adjust the alignment