Punching is normally carried out on soft steels or alloys while on harder materials special punches are required, which are subjected to increased wearing anyway.
The maximum loading necessary to punch must be markedly lower than the maximum punch compression resistance. Maximum loading can be calculated just multiplying material thickness times its shearing resistance and times the shearing perimeter.
The maximum punch compression tolerable for the punch depends on the type of steel and its hardness. For example, a crash-resistant and tempered steel can accept a compression loading of 2000 N/mm2 before breaking and can be used with specific working pressure up to 1500 N/mm2, still giving a good endurance. When ordering a punching tool, please specify thickness and type of material to be punched.
TONNAGE GENERAL FORMULA
|(P x S x K) / 28,3|
P = shape perimeter
S = material thickness
K = material coefficent
|Example: 40 (square perimeter with edge of 10 mm) x 2 (material thickness in mm) x 1,5 (K stainless steel) / 28,3 = 4,24 (tonnage)|