| Determining Tonnages For Round Holes
To Determine tonnages for hot rolled mild
steel (typically used in bar size angle iron, channels, tees and zees) with a 50,000 psi
strength, read direct from chart
#1. |
| Example: to punch a
4" diameter hole thru 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 direct from chart #2. |
| Example: to punch a
1/4" round hole in No. 10 gauge A-36 steel, the chart shows 3.2 tons pressure 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 thru 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 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.
|
| 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. |
