A student used a centre punch to mark points for drilling, but the drill bit still slipped. What is the most likely reason?
The indentation was too shallow
A centre punch makes a small cone-shaped indentation whose purpose is to give the drill point a seat to locate into before it starts cutting.
The rotating drill tip needs to drop into that seat; the depth of the dimple decides whether the tip can settle or simply skate over the surface.
If the indentation is too shallow, it offers almost no seat, so the spinning point slides across the metal before it can bite, which is exactly the slipping described.
Using too much force would tend to make the mark deeper, not shallower, so excess force is not the cause of the slip.
The wrong punch or an over-hardened punch might chip or fail to mark, but a properly placed deep mark of any suitable punch would still have located the drill.
So the fault lies in an indentation that was not deep enough to hold the drill point.
Hence, the answer is The indentation was too shallow.
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Important Questions from Marking and Marking Tools
What is the point angle of prick punch which is used for making light punch marks?
The point angle of scriber is
The angle of the punch used for witness marks is
A fitter is tasked with marking accurate parallel lines on a metal plate before cutting. He must select a divider with tips made of a suitable material for this job. Which divider tip material would be most appropriate to use to avoid rapid wear and ensure precise marking on the metal surface?
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