B961: Hollow Drill Breakage - Causes & Corrections

Indication

Cause

Correction

Cutting edge of drill bell forming and heat coloring.

DULL DRILL - Heating drill bit to point of removing temper.

SHARPEN DRILL - Reduce RPM or turning speed of drill. Increase strokes/minute to reduce time of drill in paper.

Cutting edge of drill bell forming. No heat coloring. Spiral split in drill.

DULL DRILL - Forcing drill through lift too fast.

SHARPEN DRILL - Reduce strokes/minute. Increase RPM or turning speed of drill.

Drill breaking at shank. No bell forming, no heat coloring. Chips free in drill.

Drill being deflected. Breakage due to fatigue.

Check head mounting square on rail. Make drill pattern in wood stick - no paper. Make drill pattern in wood stick with paper. Note deflection on wood stick.

Chips tight in hollow drill.

DULL DRILL - Crowding drill, punching rather than cutting.

SHARPEN DRILL - Reduce strokes/minute. Increase RPM or turning speed of drill. Check for heat coloring of drill when increasing RPM.

Chips tight in hollow drill.

Drilling paper with adhesive or thermal binding material.

When drilling cycle stops, drill a couple of holes in bond paper to clear chips out of drills. Do not allow adhesive to harden.