The centre punch is made form mild steel with the point hardened and tempered so that it withstands impact with the material it is marking. It is normally used to mark the centre of a hole to be drilled either by hand or on the drilling machine.

The dot punch is a lighter and thinner version of the centre punch and is used basically for the same job. However, it is more accurately as the dot produced is smaller.

Both the centre and dot punches are used in the same way. A ball pein hammer is used to tap the head of the punch and this delivers enough force to the point of the punch to put a small indentation into the surface of the material.

TWO USES OF THE DOT PUNCH AND CENTRE PUNCH

1. A hole is to be drilled in this material. One possible danger is that the hand drill will slip when drilling first starts. If a centre punch is used to mark the point of drilling, slipping is unlikely to happen.

2. The copper is to be cut along the line. To make it easier to see a dot punch had been used to emphasise the line.

As pressure is applied by hand to the punch, the internal springs absorb the compressive force, until it reaches a ‘tipping point’. The stored energy is then released, forcing the tip of the punch into the surface of the metal. This leaves an indentation in the surface.

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