Drilling accuracy

Twist Drill Troubleshooting Guide
Hole Problems:
Hole expansion
Irregular hole size
Low position accuracy
Hole perpendicularity
Bad cylindrical accuracy
Poor surface finish
Bad cylindrical shape
Drill Problems:
Drill breakage
Chipping of corner edge
Chipping of cutting edge
Abnormal wear on corner part
Large wear and chipping, crushing of the chisel edge
Chipping of margin
Margin build-up
Tang breakage
Noise of chattering
Chip rolled around drill
One-side wear

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