This chart is calculated according to the mat erial power of tensile strenght &b=450N/mm2 The bending power can be got according to the proportion while different kind of material is being bent .when L=1m.the numerical value in the chart is the bending power.
e.g.S=4mm L-1m V=32mm
By Consulting the chart P=330kNCalculating Formala P=650s2L/v(kN)S-the thickness of the plate to be bent(mm)L-the width of the plate to be bent(m)V-the size of the opening of the lower die(mm)