Notching Force Calculator
Estimate sheet metal notching force from notch perimeter, material thickness, shear strength, corner radius, blade rake, clearance, simultaneous cut length, and press tonnage.
Notching Force Results
Calculation Breakdown
| Material | Typical shear strength | Metric equivalent | Notching note |
|---|---|---|---|
| Aluminum 5052-H32 | 23,000 psi | 159 MPa | Good forming alloy, modest tonnage. |
| Aluminum 6061-T6 | 30,000 psi | 207 MPa | Needs clean clearance to limit cracking. |
| Galvanized sheet steel | 40,000 psi | 276 MPa | Watch coating buildup on die edges. |
| Mild steel / CR sheet | 45,000 psi | 310 MPa | Common baseline for shop notching. |
| 304 stainless steel | 75,000 psi | 517 MPa | High load; use extra press margin. |
| 316 stainless steel | 80,000 psi | 552 MPa | Tougher cut with more edge wear. |
| Copper C110 | 28,000 psi | 193 MPa | Ductile; burrs grow with excess clearance. |
| Cartridge brass | 35,000 psi | 241 MPa | Cuts cleanly with sharp tooling. |
| Material group | Clearance per side | Corner radius guide | Expected edge |
|---|---|---|---|
| Soft aluminum | 5% to 8% of thickness | 0.5t minimum relief | Low load, burr sensitive. |
| Mild and galvanized steel | 7% to 10% of thickness | 0.5t to 1.0t relief | Balanced fracture and burnish. |
| Stainless steel | 9% to 12% of thickness | 1.0t relief preferred | Higher tonnage and springback. |
| Copper and brass | 5% to 8% of thickness | 0.5t relief minimum | Ductile edge, manage rollover. |
| Notch type | Perimeter model | Best use | Load behavior |
|---|---|---|---|
| Right-angle corner | A + B with radius relief | Box blanks and flanges | Peak rises at the inside corner. |
| Rectangular edge notch | Width + 2 x depth | Tabs, slots, and wire exits | Longer perimeter than a corner notch. |
| V notch | Leg A + leg B | Bend relief and layout marks | Tip radius strongly affects load. |
| Custom perimeter | Measured developed length | Compound or shaped tools | Use actual simultaneous cut length. |
| Job | Thickness | Perimeter | Approximate peak load |
|---|---|---|---|
| 20 ga galvanized HVAC corner | 0.036 in | 2.0 in | About 1.6 US tons before rake. |
| 16 ga mild steel bracket | 0.060 in | 3.0 in | About 4.1 US tons before rake. |
| 3 mm 5052 aluminum chassis | 3.0 mm | 80 mm | About 4.3 metric tonnes before rake. |
| 11 ga stainless guard plate | 0.120 in | 3.5 in | About 15.8 US tons before rake. |
This notching force calculator matters because getting tonnage wrong can stall a press mid-run or wreck a die in a single cycle. Even with experience, forces at work often surprise an operator who may think the cut appears small even though actual force is much higher. Understanding what material resists as that blade hits is usually the difference between a clean edge and burring mess.
Sheet metal shear notching take material off sheet edges which allows corners to bend shut without tearing. When bending parts like stainless steel sink or an HVAC corner, base load depends on length of the edge that is sheared. Notching a basic right angle looks simple enough; however, that inner corner concentrate stress. Because it is hard for material to flow, sharp radii smaller than a quarter of material’s thickness increase required force. The calculator adjusts those geometry changes in the background, but a bit more radius around that inside corner will pay off in longer tool life and reduced tonnage.
Why This Calculator Is Important
All that aside, it comes down to materials. Predictable mild steel with shear strength of approximately 45,000 psi acts one way. Jump up to something like 304 stainless and you’re into loads almost double then. And aluminum is easy to cut, but if you’re not right on clearance, you’ll gall it. The edge rolls up instead of breaking off cleanly.
Why does clearance matter? It’s not simply a pretty detail. Too tight and you get excessive burrs and heat, too loose and the edge rolls instead of fracturing cleanly. This means there is sweet spot for each alloy, and shop experience help keep some go-to numbers handy.
One of these low-key variables with big rewards has always been blade rake. Angling your cutting edge up a degree or two distribute the impact across more distance instead of slamming it all at once. Total energy spent on the cut remains about the same but peak tonnage drop. On small presses where real risk is momentary overload, this makes it possible to try out various rake angle and watch the load respond.
People also underestimate simultaneous cut length. When all sides engage around perimeter of a part simultaneously, you have maximum force; staggered entry reduces that peak. Variation in materials and tool wear also reduce your safety buffer, so throw in some reasonable operating margin as well. So shops should of overrate their presses by more than they calculate.
This means typical errors usually happen because people do not account for how corner radii affects load concentration and follow handbook tensile values instead of shear strength. Some fail to realize that a lowered rake reduce force instantly. However, tool life is governed by full perimeter tonnage. The calculator breaks it out to allow you to address both factors.
In the end, notch is all about controlled fracture rather than brute force. Finding the right balance between thickness, perimeter, and shear, along with knowing the best rake and clearance, make for a press that runs smoothly. Taking a few minutes to check numbers prior to stepping on the foot pedal will pay you back nearly every time in spades.
