to form a piston 10 as described above fig3 shows an exemplary embodiment of a ring shaped upper piston part 111 punched out of a semi finished product 22 the upper piston part 111 has a circumferential lower recess 127 that forms part of a circumferential cooling channel in the finished piston see the cooling channel 21 in fig1 the recess 127 is formed in that the punching tool is provided with a corresponding embossing shape in known manner therefore the recess 127 is formed at the same time with the punching process the central opening 113 of the ring shaped upper piston part 111 forms part of a combustion bowl in the finished piston see the combustion bowl 13 in fig1 of course the same holds true analogously also for production of a blank from the semi finished product 22 fig4 shows another exemplary embodiment of a ring shaped upper piston part 211 punched out of a semi finished product 22 the upper piston part 211 also has a circumferential lower recess 227 that forms part of a circumferential cooling channel in the finished piston see the cooling channel 21 in fig1 the upper piston part 211 furthermore has a circumferential outer recess 228 that forms part of a piston ring groove in the finished piston see the piston ring groove 14 in fig1 the recesses 227 and 228 are formed in that the punching tool is provided.