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Franklinton, LA | There are 3 things I always keep in mind when punching holes in steel.
First, the die should be bigger than the punch by 1.10 - 1.15 times the thickness of the steel. For example, if you are punching holes in 3/8" thick steel the die should be 0.038 - 0.056" larger than the punch. If the die is too large the hole will be cone shaped and not very smooth. The punch life will be reduced and it could break if the die is smaller.
Second, when punching mild steel, it will take about 30 tons per square inch to shear the metal. For example, it will take about (3.14 X 9/16" X 3/8" X 30 tons/square inch) or 19.9 tons to punch a 9/16" hole in 3/8" steel. You can punch holes in medium carbon steel but it will take more tons. You will hear a loud popping sound and the press will jump when punching the hole. Also, the punch and die life will be reduced.
Third, the punch dia. should exceed the thickness of the steel. Calculate the force per square inch on the punch to see why.
For more information, you can buy an older edition of "Machinery's Handbook" on EBay for a very reasonable price.
Edited by DRester 11/24/2021 17:51
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