Oversize Hole
1. Unequal point angle
2. Unequal length of lips
3. Machine spindle running out of true
Drill Breakage
1. Feed rate too high
2. Drill is dull
3. Point incorrectly ground
4. Flutes chocked with swarf
5. Work not held rigid
6. Insufficient lubricant
7. Machine spindle running out of true
8. Slipping chuck
Breakage of Tang
1. Fit between taper shank and socket imperfect,
possibly due to:
a. swarf or
b. damaged or badly worn socket
Chipped Cutting Edges
1. Feed rate too high
2. Lip clearance too high
Rapid Wear of Outer Corners
1. Speed too high
2. Insufficient lubricant
Unequal Chips
1. Unequal length of lips
2. Point incorrectly ground
