HSS Twist Drill Bits -Trouble Shooting Guide

• Irregular hole size

• Chipping of corner edge

• Low position accuracy

• Chipping of cutting edge

• Hole perpendicularity

• Abnormal wear on corner part

• Bad cylindrical accuracy

• Large wear and chipping, crushing of the chisel edge

• Poor surface finish

• Chipping of margin

• Bad cylindrical shape

• Margin built-up

• Tang breakage

• Noise of chattering

• Chip rolled around the drill

• One side wear

Hole

Type of trouble

Reasons for the trouble

Solutions

Hole expansion

Run out of drill when attached to the machine

Check holder and/or select another one

Loose hold

Check run out after fixing to the chuck

Non-symetric point angle

Regrind correctly

Different lip height

Check preciseness after reground

Run out of chisel edge

Irregular hole size

Non-symetric point angle

Regrind correctly

Large lip height

Check precision after regrind

Run out of chisel edge

Margin wear is large

Large run out after attached to the machine

Check holder and select another one

Loose hold

Check run out after fixing to the chuck

Low work holding rigidity

Feed rate to high

Decrease feed rate

Not enough lubrication

Use drill with an oil hole

Large run out when attached to the machine

Check holder and/or select another one

Large spindle run out

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

Excessive tool wear

Regrind

Low position accuracy

Increase position accuracy (EX-Gold drill)

Non-symetric point angle

Regrind correctly

Large lip height

Check precision after regrinding

Run out of chisel edge

Not enough drill rigidity

Increase drill rigidity

Drilling surface is not horizontal

Work piece must be horizontal

Poor alignment (for lathing)

Make a center hole. Check alignment

Non-symetric point angle

Regrind correctly

Large lip height

Check precision after regrinding

Run out of chisel edge

Large run out after attached to machine

Check hole and/or select another one

Loose hold

Check run out after fixing to the chuck

Low work holding rigidity

Relief angle is too large

Regrind correctly

Low drill rigidity

Use carbide drill or larger web drills

Poor surface finish

Poor regrinding

Take off all the wear

Not suitable coolant for the material

Change supply method; increase volume

Not enough coolant

Select higher coolant quality

Large run out after attached to machine

Check holder and/or select another one

Loose hold

Check run out after fixing to the chuck

Feed rate is too high

Reduce feed rate

Excessive tool wear

Regrind correctly

Build up on margin is too large

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)

Bad cylindrical shape

Non-symetric point angle

Regrind correctly

Large lip height

Check precision after regrinding

Run out of chisel edge

Large margin wear

Feed rate is too low

Increase the feed rate

Drill

Type of trouble

Reasons for the trouble

Solutions

In accurate machine

Increase the rigidity of machine, drill and work clamping

Work material deformation

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

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

Chipping of cutting edge

Large run out after attached to machine

Check holder and/or select anothre one

Loose hold

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

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

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

Chipping of margin

Bush diameter is too small

Select correct bush diameter or select drill with chip breakers

Chip packing between drill & bush

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

Change drill or the cutting conditions

Ductile material

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

Noise of chattering

Relief angle is too big

Grind a smaller relief angle

Low rigidity of the tool

Use drill with high rigidity

Chip rolled around the drill

Low extended and curly chips

Change drill and cutting conditions

Chips are stubbed in the flute

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