Punch (tool)

A grain is a tool that is used to provide metal or plastic parts with a small depression, the so-called grain. He is of hardened tool steel, has a hardened tip and a shank. In general, the tip has an angle of 60 ° or 90 °.

Application

When pre-punching or center punching the tip of the center punch is driven by a light hammer blow into the workpiece. This results in a small depression in the form of a crater, which is referred to as grain. If a deeper grit is needed, a grain can be applied retrospectively with a peak of 60 °. The accuracy of the graining depends on the accuracy of marking.

A special form of the centering center punch forms. The grain is out here in the axle extension of a perforated hollow cone inside which it protrudes. So it is possible, precisely to punch the smooth end faces of cylindrical workpieces without first marking the center, as the bell centered by its conical shape itself.

Hole preparation

Most of the grain is used to give a drill of the first guide ( centering). Without grain, the drill tends to when scheduling the work for aimless walking, ie it slides uncontrolled over the surface, so that no dimensionally accurate drilling position is possible. In purely mechanical drilling, eg with NC - controlled machine tools, a center drill or a multi- drill- drill is used for this task instead of a center punch. One should ensure that the tip of the center punch is intact, otherwise is not deep enough the notch in the material to be processed and so the centering does not work anymore when graining.

Contour marking

In addition to the preparation hole aggregates are used as precision points for example on sheet metal to provide a robust and accurate guidance for the following operations. Here is also a double peak grains can be used to make more effective the work with long contours. The distance between the two peaks located at a shaft depends on the fineness / coarseness of the scribe work. This application has become rare nowadays, because providing for the creation of contours rather numerically controlled machine tools.

" Grains " is not to be confused with " live center ", a device for turning machines. The function is fundamentally different.