Busbar punching force calculator

Punching force is the sheared perimeter multiplied by material thickness multiplied by shear strength. For a round hole the perimeter is π × d; for a shaped hole it is the developed perimeter of the profile. Shear strength varies with material and temper, so a half-hard bar needs appreciably more force than an annealed one of the same section. Two figures are worth knowing. For copper, measured shear strength runs at 0.65 to 0.70 of tensile strength, and this calculator uses measured shear values throughout. Aluminium covers a wide range: soft 1xxx conductor grades sit near 60 to 80 N/mm², while 6101-T6 is roughly double that, which is why the grades are listed separately here. Machine sizing follows the largest hole in the thickest, hardest bar in the drawing set, with margin; the recommended rating includes 25 percent.

F = perimeter × thickness × shear strength