Drill held not correctly

Work is not rigidly he

Clearance angle is incorrect

Flutes are clogged with chips

Reaming

Spot facing

Counter boring

Counter sinking

Cutting edge will be blunt

Cutting edge will not be sharp

Cutting edge will become weak

Cutting edge will not cut material

Drill will break

Drills are over heated

Drill make rough hole

Over sized holes are made

Grade

Grain size

Type of bond

Type of abrasive