## Stamping Press

Factory Direct Sale

# How to Calculate Punching Force (Formula & Tonnage Calculator)

## Punching Force Calculation Formula

If you punch round holes or square holes, or some other forms of holes through a given thickness of metal, you just want to know the force required to punch a hole in steel.

You can calculate the punching tonnage been required with the help of the following punching force calculation formula (blanking force formula):

Punching Force (KN) = Perimeter (mm) * Plate Thickness (mm) * Shear Strength (kn / mm2)

Converted into metric tons: dividing the result of KN by 9.81

• Perimeter: add up the continuous line forming the boundary of a closed geometric figure.

• Thickness: the thickness which will be piecing through by the punching mold.
• Shear Strength: The physical properties of the plate, determined by the material of the sheet and can be found in the material manual.

Common materials’ shear strength are as follows: unit: KN/mm2

 Aluminum Brass Low Carbon Steel Stainless Steel 0.1724 0.2413 0.3447 0.5171

For various shear strength table, you can check out the following post:

e.g: If punching one square hole in the 3mm thickness low-carbon steel plate, side length 20mm, you will get:

• Perimeter = 20×4 = 80mm
• Thickness = 3mm
• Shear Strength = 0.3447kn/mm2

Punch Force (KN) = 80 x 3 x 0.3447 = 82.728 KN Convert into tonnage: 82.728 KN ÷ 9.81 = 8.43 Ton

For more details about the shearing strength including how to calculate it, you can refer to the answer from Wikipedia.

## Punching Force Calculator

P.S: If you want to calculate hydraulic press tonnage, you can use our hydraulic press tonnage calculator.

## Punch And Die Clearance

The clearance between punch and dies is represented by the total difference, which is one of the critical factors in the punching process.

For example, when using ø12 upper die and ø 12.25 lower die, the optimal clearance is 0.25mm.

Improper clearance will reduce the die service life, or burrs and lead to secondary cutting, the irregular opening will increase the demounting force, etc.

Besides, the die clearance is subject to the material and thickness, generally, for carbon steel plate, 12%-18% of the thickness is best.

If no special requirements in CNC punch, you can refer to the following table for selecting the die clearance:

### Punch Machine’s Die Clearance Table

Plate ThicknessMaterial
Mild SteelAluminumStainless Steel
0.8-1.60.15-0.20.15-0.20.15-0.3
1.6-2.30.2-0.30.2-0.30.3-0.4
2.3-3.20.3-0.40.3-0.40.4-0.6
3.2-4.50.4-0.60.4-0.50.6-1.0
4.5-6.00.6-0.90.5-0.7

### 62 thoughts on “How to Calculate Punching Force (Formula & Tonnage Calculator)”

1. Dear sir, these site is very nice for quick learn can you please provide information about bolier, reactor, pressure vessel and heat exchanger manufacturing.

2. Thank you for this site, please can you send information about generated side force in plate metal chipping process.

3. we trial very simple example, for now, do piercing in 10 mm thickness and 10 dia mm this is HRC sheet.
= Thickness X Perimeter X tensile Stress
=10*31.4*410
=128740 kg
=128 tonnage machine is needed. but we all think Safety of factory also. we can consider SOF 1.2
=155 tonnage machine we needed for the piercing.

4. I AM DOING PUNCHING IN HRC SHEET 8MM THICK . DOING IT ON 50 TON MECHANICAL PRESS
PERIMETER OF HOLE IS 104 AND I AM DOING TWO SAME HOLES AT ONCE .
ACCORDING TO THEORY TONNAGE REQUIRED IS
F- 104*2X8X.3441/9.81
F=58.4689

IS THERE ANY THING WRONG IN MY CALCULATION OR THE MACHINE HAS MORE CAPACITY THAN DESCRIBED.

1. The result calculated by the formula is the theoretical value. In practical use, the press force of the selected machine should be larger than the theoretical value. 1.2/1.5X will be better.

5. Dear Sir, How do I punch 1 mm holes (Multiple holes) in 1 mm thick SS 316 sheet. The punches available are unable to do this. Do we need Tungsten or Silicon Carbide punches?