is the total force required by the machine to punch a hole in metal based on the material thickness, type and hole shape.
Calculating the cutting force is very important for checking whether the machine has enough tonnage to do the job without damaging the machine itself.
A common formula to determine the cutting force is by multiplying the material shear strength with the material thickness and the perimeter of the punch tool.
Formula for finding the cutting force required to pierce or blank metal.
Fc = Cutting Force (Kgf)
t = Material thickness (mm)
S = Shear strength of material (Kg/mm2)
L = Length of cut or perimeter (mm)
Fc = L x t x S
Listed below are shear strength values of some materials to calculate the cutting force.
||Shear Strength (kg/mm2)|
|High carbon steels
0.6 to 1% carbon
|Low carbon steels
0.1 to 0.2% carbon
|Med, carbon steels
0.3 to 0.4% carbon
Shear strength = 0.75 x Tensile strength
The face of the punch tip may be ground flat, roof-topped, or concave to reduce the amount of cutting force.
Cutting clearance plays an important role in the quality of punched hole or blank.