in advance to determine reference values if this correlation is known then the length of the chisel 10 can be determined through measurement integration of the respective head volume currently present this method however is based on the assumption that the chisel tip 11 has a cross section that increases in the longitudinal direction of the chisel the integration method is preferably established so that even with completely worn chisels 10 the integration does not extend into the head region because erosion in the head region distorts the result this method has the advantage of not requiring a reference point that is subject to little wear sometimes such a reference point is not present or is very difficult to identify in order to determine the asymmetry factor of the wear it is possible for example to calculate the average between the upper and lower contour lines fig7 shows the contour lines and their averages for a new chisel tip 11 for a chisel tip 11 with rotationally symmetrical wear r 1 and for a chisel tip 11 with non rotationally symmetrical wear r 2 it is clear that with the asymmetrically worn chisel 10 the average line m 2 of the two contour lines has a certain slope in relation to the longitudinal axis of the chisel the angular position could.