How to calculate the tonnage for a punch press

Written by andy pasquesi
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How to calculate the tonnage for a punch press
A hydraulic piston (Thinkstock Images/Comstock/Getty Images)

In metalworking, a punch press refers to any device that cuts holes into a sheet of material. While hand-operated models still exist, punch presses commonly employ automated computer-numerical control (CNC) systems coupled will hydraulic pistons capable of a generating hundreds of tons of force. To determine the force or tonnage that a press's hydraulic system must exert in order to cut metal with a particular die, you need to consider shear strength and thickness of the metal as well as the circumference or perimeter of the die.

Skill level:

Things you need

  • Measuring tape (ribbon-style)

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  1. 1

    Determine the material factor for the target sheet metal material (see Resources).

  2. 2

    Measure the entire perimeter of the die in millimetres with the measuring tape.

  3. 3

    Measure the thickness of the target sheet metal in millimetres.

  4. 4

    Determine the shear factor for the surface of the die (see Resources).

  5. 5

    Multiply the material factor by the die's perimeter.

  6. 6

    Multiply the result from Step 5 by the sheet metal's thickness.

  7. 7

    Multiply the result from Step 6 by the die's shear factor. This will give you the force required by the punch press, in kilonewtons (kN).

  8. 8

    Multiply the result from Step 7 by 0.102 to convert its units from kilonewtons to metric tons.

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