members 14 cannot become clogged with waste material or are easy to clean where applicable fig2 to 27 show various embodiments of chisel holder changing systems in which the above described chisels 10 can be used together with the nut 30 according to fig4 to 7 in these drawings for the identification of identical or equivalent components the same reference numerals as above are used reference may therefore be made in full to the statements above fig2 shows a tool holder changing system having a tool holder 40 which carries at a base portion 41 an integrally formed plug type attachment 48 a cylindrical attachment 42 is further formed on the base portion 41 in the region of the cylindrical attachment 42 a counter face 44 corresponding to the support face 15 is again constructed in accordance with the chisel holder 40 according to fig8 to 11 in the base portion 41 and the cylindrical attachment 42 there is formed a chisel receiving member 45 which terminates in a sealing portion 46 the sealing portion 46 is again adjoined by the holder receiving member 47 in which the nut 30 according to fig4 to 7 is inserted in this instance the nut 30 again has a securing portion 33 with blocking faces 34 the blocking faces 34 cooperate.