Tons to Punch Round Holes in Mild Steel Cold
Diameter
Inches
Thickness - Inches
.015 .020 .032 .063 .074 .090 .125 .188 .250 .313 .375 .438 .500
.188 .27 .35 .57 1.1 1.3 1.6 2.2 3.3 N/A
.250 .35 .50 .75 1.5 1.7 2.1 2.9 4.4 5.9 N/A
.313 .44 .59 .94 1.9 2.2 2.7 3.7 5.6 7.4 9.2 N/A
.375 .53 .70 .81 2.2 2.6 3.2 4.4 6.6 8.8 11 13 N/A
.438 .62 .83 1.3 2.6 3.1 3.7 5.2 7.8 10 13 15 18 N/A
.500 .71 .94 1.5 3.0 3.5 4.2 5.9 8.9 12 15 18 21 24
.625 .90 1.2 1.9 3.7 4.4 5.3 7.4 11 15 18 21 26 29
.750 1 1.4 1.6 4.4 5.2 6.4 8.8 13 18 22 27 31 35
1.00 1.4 1.9 3 6 7 9 12 18 24 30 35 42 47
1.25 1.8 2.4 3.8 7.4 8.8 11 15 22 29 37 44 50 59
1.5 2 2.8 3.2 8.8 10 13 18 26 36 44 53 62 71
1.75 2.5 3.3 5.2 10 12 15 21 31 41 52 62 72 82
2 2.8 3.8 6 12 14 18 24 36 48 59 71 83 95
2.50 3.6 4.8 7.6 15 18 22 30 44 58 74 88 103 118
3.00 4.2 5.7 9 18 21 27 36 54 72 89 106 124 141
3.50 5 6.6 10 21 24 30 42 62 82 103 124 145 164
4 5.6 7.6 12 24 28 36 48 72 96 118 141 165 189

To calculate the force to punch holes in metal you determine the cross section in shear and multiply it by the shear strength of the metal. The formula is Perimeter times thickness times shear. For round holes in steel this is Diameter * PI * 30. Thirty tons being the approximate shear strength of mild steel plus an allowance for friction. Tons are used to aid in press selection and rating. The practical limit for depth of punching cold is the diameter of the hole.

punch_force.js
Units = Inches : Material = Steel
Hole Diameter In.
Material Thickness
Shear Area
Force Tons

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