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Broken outer Corners
(a) Possible Cause
Drilling thin material particularly when not properly supported.
Solution
Use a sheet metal drill and clamp the workpiece securely.
(b) Possible Cause
Using a 2 flute drill to enlarge the diameter of an existing hole.
Solution
Only core drills should be used for this purpose.
Chipped or Broken Lips
(a) Possible Cause
This is usually caused by excessive lip clearance angles behind
the cutting edge.
Solution
Check that the lip clearance is as per information on page 24/
25.
Oversized and Out of Round Holes
(a) Possible Cause
Unequal point angles.
Solution
This usually results when hand grinding the point. Use a point
grinding fixture or machine.
(b) Possible Cause
Unequal cutting edge length (lip height).
Solution
When re-grinding ensure that the same amount of material is
removed from both flanks.
(c) Possible Cause
Loose spindle or worn drill sleeve.
Solution
Use equipment which is in good condition.
(d) Possible Cause
The workpiece moves.
Solution
The workpiece must be securely clamped.
