CustomPartNet
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August 11, 2026
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Updated August 11, 2026
Once you know the tonnage a bend will require, the next step is finding a shop with a press brake that can actually deliver it, along with the tooling and volume experience your part calls for. Capacity, tooling inventory, and finishing capabilities all vary quite a bit between fabrication shops, and matching those details to your project early on can save a lot of back and forth later. Sample parts are also worth requesting if you're unsure whether a supplier's typical work lines up with your tolerances and finish requirements. Browse our supplier network on the right to compare qualified fabricators and request quotes.
Most sheet metal bends are formed on a press brake, a machine that uses an upper tool called the punch and a lower tool called the die to force a flat sheet into an angled shape. The sheet sits over the die, held in place by a back gauge, while the punch drives downward under hydraulic power. How much force that punch needs to apply depends heavily on which bending method is being used, and getting the tonnage estimate wrong can mean running your part on a machine that can’t make parts that meet your spec, or paying for far more press than the part requires.
CustomPartNet offers two widgets, the V-Bending Force Calculator and the Wipe Bending Force Calculator, built to help you with these calculations. They cover the two most common bending methods used in production, and different inputs are required because the two processes distribute force across the sheet in different ways.
V-bending is the most widely used bending method because the tooling is simple: a V-shaped punch presses the sheet into a matching V-shaped groove in the die. If the punch stops short of the bottom of the groove, leaving a gap of air underneath the sheet, it's called air bending. If the punch drives the sheet all the way to the bottom of the die cavity, it's called bottoming, which reduces springback at the cost of requiring a heavier press.
The V-Bending Force calculator asks for:
Sheet thickness
Bend length
Die opening
Ultimate tensile strength of the material
The die opening matters because it sets the width of the "V" the sheet is being pushed into. A narrower opening concentrates the load over a smaller area and drives tonnage up, while a wider opening spreads the force out and reduces it. Most shops run die ratios (the die opening divided by sheet thickness) somewhere between 6 and 18.
Wipe bending, sometimes called edge bending, works differently. The sheet is clamped between a wipe die and a pressure pad, and only the portion of material extending past that clamp is bent, by a punch pressing down against its edge. Because the die itself has a fixed radius rather than a V-shaped groove, wipe bending is often the better choice when a part needs a sharp, consistent radius on a single bend angle, particularly near an edge or feature where a full V-die wouldn't fit.
The Wipe Bending Force calculator asks for:
Sheet thickness
Bend length
Die edge radius
Punch edge radius
Ultimate tensile strength of the material
Instead of a die opening, the geometry here comes from the two radii. A tighter die edge radius increases the required force because the sheet has to bend more sharply over a smaller curve, while a more generous radius eases the load.
Neither method is universally "better." The right choice usually comes down to tooling flexibility versus repeatability.
V-bending tends to win when a job involves multiple bend angles or when tooling needs to be reused across different parts, since a single V-die can produce a range of angles just by changing how far the punch travels. It's also generally the lower-cost tooling option, which matters for shorter production runs or prototype work.
Wipe bending tends to win when a design calls for a tight, consistent radius near an edge, when a part geometry makes it awkward to fit a V-die close enough to the feature being bent, or when a single bend angle will be run at high volume and dedicated tooling makes sense. Because the die and punch are matched to one specific radius, wipe bending typically produces tighter repeatability from part to part.
Consider a 0.100 inch mild steel bracket with a 10 inch bend length and a 90 degree bend, using a material with an ultimate tensile strength around 60,000 psi.
Running that part through the V-Bending Force calculator with a 0.8 inch die opening (die ratio of 8) returns a required force in the neighborhood of 5 tons. That figure comes from the standard relationship between bend length, sheet thickness squared, tensile strength, and die opening that governs V-bending, and it's why doubling the sheet thickness has such an outsized effect on tonnage compared to doubling the bend length.
Running the same bracket through the Wipe Bending Force calculator, using a 0.125 inch die edge radius and a 0.06 inch punch edge radius, typically returns a noticeably lower figure, often in the 2 to 3 ton range for this geometry. The difference comes down to how each process engages the sheet: V-bending forces the full width of material into a V-shaped groove, while wipe bending only stresses the section of sheet extending past the clamped die and pressure pad. Exact numbers will shift with your specific radii and material, which is exactly why it's worth running your own part through both calculators before committing to a machine.
The die opening controls how the load spreads across the sheet during the bend. A narrower opening concentrates force over less material, so tonnage climbs, while widening the opening reduces the pressure needed to complete the bend. This is why die ratio is one of the most common variables shops adjust when a part is running over their press capacity.
Generally yes for the same sheet thickness and bend length, since wipe bending only loads the section of material beyond the clamped die and pad rather than the full sheet width. But a very tight die edge radius can push wipe bending tonnage up considerably, so it's worth checking both calculators rather than assuming.
At best, the punch simply won't drive the sheet to the desired angle. At worst, running a part on an undersized press can stall the machine or place excessive strain on the tooling and ram. Estimating tonnage ahead of time, and building in a reasonable safety margin, helps avoid both outcomes.
Thickness has a much larger effect. In V-bending, force scales with the square of the sheet thickness, so a jump from 0.075 inches to 0.100 inches increases tonnage far more than a proportional increase in bend length would.
Yes. Both calculators take ultimate tensile strength as an input, so aluminum, stainless steel, and other common sheet materials can all be run through them by entering the correct tensile strength for the grade being used.
Most standard V-die tooling falls between a 6:1 and 18:1 ratio of die opening to sheet thickness. An 8:1 ratio is a reasonable starting point for general-purpose air bending, and the calculator lets you adjust it to see how sensitive your tonnage estimate is to that choice.
In addition to bending force, CustomPartNet's Bend Allowance Calculator and Bending Springback Calculator help with flat pattern development, as well as compensating for the sheet's tendency to spring back after a bend. A calculator for deep drawing force is also in the works.
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