Use This Flange Formula for Sheet Metal Forming (Updated for 2024)

Last updated on January 2nd, 2024 at 12:44 pm

In custom sheet metal fabrication, a flange is a feature consisting of a face with a bend that connects to an existing face. Flanges can add strength to precision sheet metal parts and provide a more finished edge along the straight side of a part.

While bending flanges with standard sheet metal forming methods might seem straightforward, we frequently receive designs with flange measurements that are too short to be successfully fabricated.

Why Flange Height Mattersflange formula

At Approved Sheet Metal, we bend flanges using a v-shaped die on our press brake machines. We lay the material across the die, ensuring that there is ample material on both sides to provide resistance when the press comes down. As the press bends the material into shape, it creates three touchpoints: on the right, left, and center-bottom, forming a "v."

If the flange height is too short, there won't be sufficient material to lay all the way across the v-shaped die. The material will slip out of position when pressed, compromising the flange.

Often, customers are unaware that their designs include insufficient flange heights. While our team of expert engineers is always here to help you assess your designs for manufacturability, we also want to make flange design easier so that you can avoid unneeded back-and-forth with your sheet metal shop.

The Perfect Fit Flange Formula

To ensure your precision sheet metal fabricator can make your parts correctly, we developed a formula that guarantees flanges will always be the right height.

4x Material Thickness + Bend Radius = Minimum Acceptable Flange Height

Pro tip: Jot that formula down or bookmark this blog post so you can return to it for future reference! 

Now, let's get into why this formula works.

  • Die measurements. We derived this formula from the equation we use to identify the correct die measurements: a die must be 6x the material thickness to work. So, we considered that half of that (3x) plus the bend radius would make the flange height just right. Except, just right doesn't allow for any buffer. If unforeseen issues occur, such as slippage in the machine, we might not have enough material to bend the flange. Plugging 4x the material thickness into the formula ensures we'll have enough height to manufacture a flange correctly and consistently.
  • Material thickness. The formula accounts for enough room to make the bend no matter what material is used. The thicker the material, the wider the die must be to hit each of the three critical contact points.
  • Bend radii best practices. Bend radius is an equally important metric when identifying flange height. Your best bet when designing formed parts is to use the industry standard bend radius of 0.030". We use 0.030" for all material thicknesses up to 0.125" (⅛") and increase the bend radius for thicker materials.

Minimum Bend and Flange Length Guidelines Sheet Metal Parts

A Solution for Shorter Flanges

Sometimes, customers need flanges shorter than the minimal acceptable flange height. If you know Approved Sheet Metal, you know we strive to find solutions to meet all of our customers' needs.
When our customers need shorter flanges, we'll start by using the same formula to create a longer flange, then use an end mill to cut the flange down to meet their specs. While this alternative is a functional option and can work for low-volume or prototype orders, it's not ideal for production work due to the multiple setups required for each part.

Cutting off a significant amount of material can also cause the material to bow, compromising part structure. And, frankly, it leads to unnecessary and expensive material waste. If you want to save time and money, avoid making your flange height too short in the first place.

Remember—you don't have to do this work alone! We’re always happy to help you update your design. Our team has decades of experience in fabrication, and we can make recommendations and adjustments that simplify the manufacturing process and get you the parts you need.

Let's work together on your next sheet metal forming project—request a quote today!

Sheet Metal Part Design for Manufacturing Tip


Bending sheet metal parts is a process that is completed by utilizing press brakes and our very skilled press brake operators. At Approved Sheet Metal, we can hold tolerances of +/- 1 degree on most bend angles. The ideal bend radius on formed parts is 0.030 in., this ensures that you can get consistent, quality parts that will maintain solid structural integrity.


Sheet Metal Fabrication Flange Formula FAQ

A flange in custom sheet metal fabrication is a feature consisting of a bent face that connects to an existing face, adding strength and a finished edge to parts. Flange height matters because it affects the successful fabrication of parts. If the flange is too short, there might not be enough material to lay across the v-shaped die during bending. This can lead to slipping during the bending process, compromising the flange's integrity.

To ensure the correct flange height, you can use the "Perfect Fit Flange Formula": 4x Material Thickness + Bend Radius = Minimum Acceptable Flange Height. This formula guarantees that there's enough material for successful bending. It takes into account die measurements, material thickness, and bend radii best practices. Using this formula helps avoid issues and ensures consistent manufacturing.

Bend radius plays a crucial role in determining flange height because it affects the bending process. Industry-standard bend radii, such as 0.030", ensure that the bending process is consistent and successful. The bend radius influences the width of the die required to achieve critical contact points during bending. Using the appropriate bend radius in your design helps maintain the structural integrity of the flange.

If you require flanges shorter than the minimum acceptable flange height, Approved Sheet Metal can provide a solution. They can use the "Perfect Fit Flange Formula" to design a longer flange and then cut it down using an end mill to meet your specifications. While this alternative works for low-volume or prototype orders, it's not ideal for production due to multiple setups and potential material waste. It's recommended to avoid designing flanges too short to save time and costs.

Approved Sheet Metal's experienced team is always ready to assist you with your design challenges. With decades of fabrication experience, they can offer recommendations and adjustments to simplify the manufacturing process and ensure you get the parts you need. Whether it's assessing your designs for manufacturability or providing expertise in flange design, their team is dedicated to helping you achieve successful outcomes in your sheet metal projects.

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