the graph of fig6 in the finish forming area 60 of the die 58 a large forming load must be applied the blanks 8a 8b and 8c the the forming load will now be described more concretely the maximum forming load exerted by the dies is represented by the following equation 4 as a sum of the equation 2 for the rough forming area 55 and the equation 3 for the o shape forming 58 in this die the load at the transitionaly area 59 is small and may be ignored a forming press 71 for the double press system is shown in fig1 and is composed of a rough o shaping press 72 and an o shaping press 75 the top die 73 and bottom die 74 of the rough o shaping press 72 have semi circular cross section and the length of the die is longer than the length of the blank this rough o shaping press 72 is substantially the same as a conventional o shaping press 21 as shown in fig4 a and 4b the o shaping press 75 is the same as the o shaping press shown in fig8 a and 8b and the die 76 has a transitionaly forming area 77 a finish forming area 78 and a re forming area 79 the length lb of the transitional forming area 77 is less than about 2 3 of the pipe diameter d and the length lc of the finish forming area 78 is less than about 1 2 of the pipe length l the the length ld of the re forming area 79 is about 0 2 to 1 0 times the pipe diameter d shaping the blank with the double press.