With a thorn - similar to countersinking , which also counts for pressing in - the tool is pressed into the surface of the workpiece . In both processes, the tool movement is straight, mostly perpendicular to the surface. There is no sliding over the surface. In contrast to countersinking, the tip of the thorn is rounded, sometimes spherical.
If the workpiece is not supported laterally, i. H. when the bowl is free , it bulges out. In the vicinity of the tool, there is a flow of material contrary to the tool movement. If the cross section of the tool is large compared to the cross section of the workpiece, the material of the workpiece deviates laterally, which results in a reduction in the height of the workpiece.
The mandrel is used as preparation for piercing , another process of pressing in, generally for the production of cavities and, in the case of variants with bulges, for intermediate products that are further processed into bevel gears .