Punch Press Calcs?

I'm building a shearing and piercing die for a customer and I want to figure out the approximate force neccesary for this die. It's got four

3/8" piercing punches and one 6" wide shear blade. This is using 1/8" thick AL stock.

So he's got a 20T press and I'm thinking we need a bigger press. So how do I figure out the tonnage needed for this die?



(remove the 4567 and it'll get to me)

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Generally, cutting length times thickness times shear strength of the material will result in cutting force required.

3/8 dia x PI x 4 =2.356 >I'm building a shearing and piercing die for a customer and I want to
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"V" notch, or an angle on the punches would drop the tonnage on those also.

Best, Steve

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Thanks for the info. Of all the books I've read, not one has had a good formulae for figuring punching forces. Also thanks for the idea of using angled or rooftop shearing. I know this reduces shearing forces but I've never known how to calculate the forces.


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First thing an apprentice toolmaker learns is cutting/punching forces.

Periphery of hole x thickness x 25 = tons in steel

Use 17 for aluminium.

Your four 3/8" holes would need a shade over 10 tons.You didn`t say what width you were shearing. Other thing to bear in mind is that press tonnage is only fully developed a short distance from bottom dead centre and some presses will run happily full time at maximum rating and some makes will not.

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