Calculator
Formula used
This calculator estimates required forming force using a common shop model:
- UTS is tensile strength (psi).
- t is sheet thickness (in).
- L is bend length (in).
- V is die opening (in).
- K reflects bend method (air, bottoming, coining).
- AngleFactor is a mild adjustment near 90°.
Always confirm with your press brake capacity, tooling ratings, and vendor charts.
How to use
- Select units and bend method.
- Pick a material, or enable custom tensile strength.
- Enter thickness, bend length, and die opening.
- Set bend angle and safety margin for extra buffer.
- Press Calculate to view results above the form.
- Use the download buttons to export CSV or PDF.
Example data table
| Material | Thickness | Length | Die opening | Method | Safety | Estimated tonnage (US) |
|---|---|---|---|---|---|---|
| Mild Steel | 0.125 in | 24 in | 1.000 in | Air Bending | 15% | ~15.0 tons |
| Stainless 304 | 2.0 mm | 500 mm | 16 mm | Bottoming | 20% | ~39.0 tons |
| Aluminum 6061 | 0.080 in | 36 in | 0.750 in | Air Bending | 10% | ~7.5 tons |
Examples are illustrative and depend on tooling and machine setup.
Professional notes on press brake tonnage planning
Press brake tonnage is the forming force needed to bend metal along a straight line. In construction fabrication, correct tonnage protects punches and dies, avoids overload, and keeps bends consistent on brackets, plates, rails, and stiffeners. It also supports safer rigging and handling by predicting load peaks during long bends.
1) Tonnage and job planning
Before cutting and drilling, confirm that the press brake can supply the required load for the planned bend length. This reduces rework, downtime, and tool damage when production moves from prototypes to batches.
2) The strongest drivers
The calculation depends mainly on material strength, thickness, bend length, and die opening. Strength differs by alloy: mild steel commonly uses about 60 ksi, stainless can be around 85 ksi, and many aluminum grades are lower, so they bend with less force.
3) Thickness effect
Force rises with thickness squared. Doubling thickness can require roughly four times the tonnage, even if everything else stays the same. This is why small gauge changes can push a job beyond a machine’s safe capacity.
4) Die opening selection
Die opening (V) is a practical lever because force is inversely proportional to V. Air bending guidance often uses V near 6–10× thickness. A smaller V increases force and can mark the part; a larger V may reduce angle control and increase springback.
5) Bend method choice
Air bending typically needs the least force, bottoming needs more, and coining may require several times the air-bend tonnage. Selecting the correct method factor improves estimates when switching between structural details and architectural trims.
Per-length output is valuable when using tooling. A brake rated 100 tons over 10 feet is not 100 tons on a 2-foot segment if load concentrates. Keep work centered and follow manufacturer guidance for safe forming.
6) Angle and setup sensitivity
Most work targets 90°, but return flanges and hems can differ. Angle changes are usually secondary compared with thickness and V, yet setup details such as tool radius, lubrication, and surface scale can shift results. Use a safety margin to cover uncertainty.
7) Verification, limits, and documentation
Compare results against machine charts that specify tonnage per length, and confirm punch and die ratings for the actual working segment. Validate with test bends and manufacturer guidance. Save CSV and PDF outputs with job travelers to repeat setups and quote confidently.
FAQs
What tonnage does the calculator output?
It returns required forming load in US tons and metric tonnes, including your safety margin. It also shows per-foot and per-meter tonnage to compare against machine charts and sectional tooling ratings.
How do I choose a die opening?
For air bending, a common starting point is a V opening about 6–10 times material thickness. Smaller openings raise tonnage and can mark the part; larger openings reduce force but may reduce angle control.
When should I use bottoming or coining?
Use bottoming for tighter angle control and repeatability when tooling supports it. Use coining only when necessary for very sharp radii or minimal springback, because it demands much higher tonnage and increases tool wear.
Why does thickness change tonnage so much?
In most shop models, tonnage scales with thickness squared. If thickness doubles, required force can rise by roughly four times, even before considering material strength and die opening effects.
Can I enter my own material strength?
Yes. Enable custom tensile strength and enter a value in ksi for imperial units or MPa for metric units. This helps when you have mill test data, special alloys, or heat-treated parts.
Is the angle input critical?
Angle usually has a smaller influence than thickness, strength, and die opening, but it can refine estimates for non-90° bends. For unusual geometries, confirm with test bends and your tooling manufacturer’s charts.
What should I do if the result is near machine capacity?
Reduce bend length, increase die opening, switch to a lower-force method, or split the bend into stages if feasible. Never exceed the press brake’s rated tonnage per length, and confirm punch and die limits before running parts.
Measure twice, verify tooling, and bend safely every time.