Drilling Errors. Causes and Solutions

Drilling Errors

In our Mechanical Engineering Education, Manufacturing Operations – Drilling section, we’re covering drilling errors and preventive measures. The problems commonly encountered during drilling are generally as follows:

We sometimes run into trouble when drilling holes. Problems like a broken drill bit, an overheating drill bit, the tip turning blue or burning, the drill not cutting through, or drilling a hole larger than the bit’s own diameter can all occur. Let’s look at the causes of these and the measures that can be taken.

Overheating

If the drill is overheating and discoloring (tempering), the likely causes and suggested solutions are:
-The drill’s speed wasn’t chosen correctly for the material type.
-The drill’s speed should be reduced.
-The drill may not be cutting well; it should be resharpened.

Burring on the Underside of the Workpiece

If the underside of the workpiece comes out with heavy burring while drilling, the likely causes and suggested solutions are:

-The drill isn’t cutting well, and the feed pressure wasn’t reduced as the drill exited the underside of the work.
-Resharpen the drill.
-Reduce the feed pressure as the drill exits.

Drill Bit Breaking

Causes of the drill bit breaking and suggested solutions:
-The feed rate may be too high
-The drill may be dull, or the material may be too hard.
-Solutions: Check each of these possibilities individually to resolve the problem.

The Drill Grabbing/Digging into the Work

The problem of the drill grabbing/digging into the work and suggested solutions:
-The workpiece is thin sheet metal, made of aluminum or brass, and more importantly, it hasn’t been clamped in a vise.
-The drill should be sharpened according to the material type and its thickness.
(The drill’s point angle should be larger for thin materials.)
-Thin sheet, brass, and aluminum parts must always be drilled while clamped
in a vise, or in a hand vise depending on the situation. Otherwise the drill bit can break.

The Drill Cutting a Hole Larger Than Its Own Diameter

The problem of the drill cutting a hole larger than its own diameter and suggested solutions:
-The drill’s cutting edges weren’t ground at equal angles and lengths. As a result, only one edge is doing the cutting.
-Solution: The drill should be reground correctly.

The Drill Running Out

The problem of the drill running out and suggested solutions:

-The chuck isn’t clean and well-maintained, or the chuck jaws may be damaged
-or the chuck isn’t gripping the drill properly
-the drill may be bent for some reason.

The Workpiece Showing Excessive Resistance to Drilling

Diagnoses for the problem of the workpiece showing excessive resistance to drilling:
The drill may be dull, or it may have hit a pearlite region within the material.
-Chips have jammed under the edge of the drill’s tip.
-If the drill has a stop, it may have hit it.

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