Determining Tonnage

For Round Holes

To determine tonnage for hot rolled mild steel (typically used in bar size angel iron, channels, tees and zees) with a 50,000 psi strength, consult Chart 1.

Example: to punch a 4″ diameter hole through 20 gauge mild steel, the chart shows 11.3 tons are required.

For ASTM A-36 steel (typically used for structural size wide flange, H and I beams, tees and zees) with a 60,000 psi shear strength, read from Chart 2.

Example: to punch a 1/4″ round hole in No. 10 gauge A-36 steel, the chart shows 3.2 tons is needed.

For other metals, select the proper multiplier from Chart 3, and apply it to the tonnage figure for mild steel shown in Chart 1.

Example: to punch a 4″ diameter hole through 20 gauge #202 stainless steel with a 1.8 multiplier, calculate as follows: 11.3 tons x 1.8 = 20.3 tons required.

For Irregular Shape Holes

To determine tonnage for punching irregular shaped holes (square, rectangular, obround, triangular, etc.) multiply the length of metal to be cut by the multiplier given for a 1″ length in Chart 4.

For example: The shear length (or total distance around a 1″ x 2″ rectangular hole) is 6″. To punch such a hole in 20 gauge mild steel multiply 6″ x 1.01 (from Chart 4) = 6.06 tons. For stainless steel, this would be 6 x 1.50 = 9.0 tons.