To determine the tonnage needed to punch a single hole with a flat faced punch:
1. Calculate the Hole Perimeter using the formulas below.
2. Find the Material Shear Strength on the table below.
3. Then use the following equation:
Flat Face Punch Force (lbs) = Punch Perimeter (inches) x Material Thickness (inches) x Material Shear Strength (lbs/in2)
To change from pounds of punch force to tons of punch force use the following equation: tons = lbs/2000
Example: To punch a 1/4" square hole in 3/16" stainless steel:
4(1/4") x 3/16" x 70,000 lbs/in2 = 13,125 lbs (6.56 tons) of punching force.
| Material | Shear Strength (PSI) | Chart Multiplier |
| Aluminum | ||
| 1100-0 | 9,500 | .19 |
| 1100-H14 | 11,000 | .22 |
| 3003-H14 | 14,000 | .28 |
| 2024-T4 | 44,000 | .88 |
| 5005-H18 | 19,000 | .38 |
| 6063-T5 | 18,000 | .36 |
| 6061-T4 | 24,000 | .48 |
| 6061-T6 | 29,000 | .58 |
| 7075-T6 | 54,000 | 1.08 |
| Brass | ||
| Rolled Sheet (Soft) | 42,000 | .84 |
| 1/2 Hard | 56,000 | 1.12 |
| Hard | 68,000 | 1.36 |
| Copper | ||
| 1/4 Hard | 29,000 | .58 |
| Hard | 43,000 | .86 |
| Steel | ||
| Mild Steel | 50,000 | 1.00 |
| Boiler Plate | 55,000 | 1.10 |
| Cold Drawn | 60,000 | 1.20 |
| 40-50 Carbon | 74,000 | 1.48 |
| Structural A-36 | 60,000 | 1.20 |
| Structural EX-TEN | ||
| (ASTM-A572) – Grade 42 | 50,000 | 1.00 |
| Grade 45 | 50,000 | 1.00 |
| Grade 50 | 55,000 | 1.10 |
| Grade 55 | 60,000 | 1.20 |
| Grade 60 | 65,000 | 1.30 |
| Grade 65 | 70,000 | 1.40 |
| Structural COR-TEN | ||
| (ASTM-A242) | 60,000 | 1.20 |
| Cold Rolled C-1018 | 60,000 | 1.20 |
| Hot Rolled C-1050 | 125,000 | 2.50 |
| Hot Rolled C-1095 | 125,000 | 2.50 |
| Hot Rolled C-1095 Annealed | 90,000 | 1.80 |
| Stainless 302 Annealed | 70,000 | 1.40 |
| Stainless 304 Cold Rolled | 70,000 | 1.40 |
| Stainless 316 Cold Rolled | 70,000 | 1.40 |
| Steel, Abrasion Resisting | 110,000 | 2.20 |
| ASTM A656 – Grade 80 | 85,000 | 1.70 |
| Hole Dia. (Inches) |
20 GA 0.0359 |
18 GA 0.0478 |
16 GA 0.0598 |
14 GA 0.0747 |
12 GA 0.1046 |
11 GA 0.1196 |
10 GA 0.1345 |
3/16 0.1875 |
| 1/8 | 0.35 | 0.47 | 0.59 | 0.73 | 1.0 | 1.2 | ||
| 3/16 | 0.53 | 0.70 | 0.88 | 1.1 | 1.5 | 1.8 | 2.0 | 2.8 |
| 1/4 | 0.70 | 0.94 | 1.2 | 1.5 | 2.1 | 2.3 | 2.6 | 3.7 |
| 5/16 | 0.88 | 1.2 | 1.5 | 1.8 | 2.6 | 2.9 | 3.3 | 4.6 |
| 3/8 | 1.06 | 1.4 | 1.8 | 2.2 | 3.1 | 3.5 | 4.0 | 5.5 |
| 7/16 | 1.23 | 1.6 | 2.1 | 2.6 | 3.6 | 4.1 | 4.6 | 6.4 |
| 1/2 | 1.41 | 1.9 | 2.3 | 2.9 | 4.1 | 4.7 | 5.3 | 7.4 |
| 9/16 | 1.59 | 2.1 | 2.6 | 3.3 | 4.6 | 5.3 | 5.9 | 8.3 |
| 5/8 | 1.76 | 2.3 | 2.9 | 3.7 | 5.1 | 5.9 | 6.6 | 9.2 |
| 11/16 | 1.94 | 2.6 | 3.2 | 4.0 | 5.6 | 6.5 | 7.3 | 10.1 |
| 3/4 | 2.11 | 2.8 | 3.5 | 4.4 | 6.2 | 7.0 | 7.9 | 11.0 |
| 13/16 | 2.29 | 3.1 | 3.8 | 4.8 | 6.7 | 7.6 | 8.6 | 12.0 |
| 7/8 | 2.47 | 3.3 | 4.1 | 5.1 | 7.2 | 8.2 | 9.2 | 12.9 |
| 15/16 | 2.64 | 3.5 | 4.4 | 5.5 | 7.7 | 8.8 | 9.9 | 13.8 |
| 1.00 | 2.82 | 3.8 | 4.7 | 5.9 | 8.2 | 9.4 | 10.6 | 14.7 |
| 1.50 | 4.23 | 5.6 | 7.0 | 8.8 | 12.3 | 14.1 | 15.8 | 22.1 |
| 2.00 | 5.64 | 7.5 | 9.4 | 11.7 | 16.4 | 18.8 | 21.1 | 29.5 |
| 2.50 | 7.05 | 9.4 | 11.7 | 14.7 | 20.5 | 23.5 | 26.4 | 36.8 |
| 3.00 | 8.46 | 11.3 | 14.1 | 17.6 | 24.6 | 28.2 | 31.7 | 44.2 |
| 3.50 | 9.87 | 13.1 | 16.4 | 20.5 | 28.8 | 32.9 | 37.0 | 51.5 |
| 4.00 | 11.28 | 15.0 | 18.8 | 23.5 | 32.9 | 37.6 | 42.3 | 58.9 |
| 4.50 | 12.69 | 16.9 | 21.1 | 26.4 | 37.0 | 42.3 | 47.5 | 66.3 |
| 5.00 | 14.10 | 18.8 | 23.5 | 29.3 | 41.1 | 47.0 | 52.8 | 73.6 |
| Hole Dia. (Inches) |
1/4 0.2500 |
5/16 0.3125 |
3/8 0.3750 |
1/2 0.5000 |
5/8 0.6250 |
3/4 0.7500 |
7/8 0.8750 |
1 1.0000 |
| 1/8 | ||||||||
| 3/16 | ||||||||
| 1/4 | 4.9 | |||||||
| 5/16 | 6.1 | 7.7 | ||||||
| 3/8 | 7.4 | 9.2 | 11.0 | |||||
| 7/16 | 8.6 | 10.7 | 12.9 | 17.2 | ||||
| 1/2 | 9.8 | 12.3 | 14.7 | 19.6 | ||||
| 9/16 | 11.0 | 13.8 | 16.6 | 22.1 | 27.6 | |||
| 5/8 | 12.3 | 15.3 | 18.4 | 24.5 | 30.7 | |||
| 11/16 | 13.5 | 16.9 | 20.2 | 27.0 | 33.7 | 40.5 | ||
| 3/4 | 14.7 | 18.4 | 22.1 | 29.5 | 36.8 | 44.2 | ||
| 13/16 | 16.0 | 19.9 | 23.9 | 31.9 | 39.9 | 47.9 | 55.8 | |
| 7/8 | 17.2 | 21.5 | 25.8 | 34.4 | 43.0 | 51.5 | 60.1 | 68.7 |
| 15/16 | 18.4 | 23.0 | 27.6 | 36.8 | 46.0 | 55.2 | 64.4 | 73.6 |
| 1.00 | 19.6 | 24.5 | 29.5 | 39.3 | 49.1 | 58.9 | 68.7 | 78.5 |
| 1.50 | 29.5 | 36.8 | 44.2 | 58.9 | 73.6 | 88.4 | 103 | 118 |
| 2.00 | 39.3 | 49.1 | 58.9 | 78.5 | 98.2 | 118 | 137 | 157 |
| 2.50 | 49.1 | 61.4 | 73.6 | 98.2 | 123 | 147 | 172 | 196 |
| 3.00 | 58.9 | 73.6 | 88.4 | 118 | 147 | 177 | 206 | 236 |
| 3.50 | 68.7 | 85.9 | 103 | 137 | 172 | 206 | 241 | 275 |
| 4.00 | 78.5 | 98.2 | 118 | 157 | 196 | 236 | 275 | 314 |
| 4.50 | 88.4 | 110 | 133 | 177 | 221 | 265 | 309 | 353 |
| 5.00 | 98.2 | 123 | 147 | 196 | 245 | 295 | 344 | 393 |
Single Hole Punching—When using a press for single round hole punching, refer to the chart above to determine the amount of force (tonnage) required to pierce a given hole. This chart is based on punching mild steel—50,000 PSI shear strength using flat face punches only.
Example: To pierce a 15/16" diameter hole through 10 gauge mild steel, the force required would be 9.9 tons.
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