How Can You Determine the Correct Bend Allowance for a Sheet Metal Press Brake?

  • By:Metmac
  • 2024-06-11
  • 5

In the realm of sheet metal fabrication, achieving precise and consistent bends is paramount. Determining the correct bend allowance for a press brake is a crucial step in ensuring the accuracy and quality of the finished product. This article delves into the factors that influence bend allowance and provides a comprehensive guide to calculating it accurately.

Material Properties

The material properties of the sheet metal play a significant role in determining the bend allowance. Different materials exhibit varying degrees of elasticity and ductility, which affect the amount of material that needs to be compensated for during bending. Softer and more ductile materials, such as aluminum, require a smaller bend allowance than harder and less ductile materials, such as steel.

Bend Radius

The bend radius is the distance from the neutral axis of the sheet metal to the inside edge of the bend. A larger bend radius requires a larger bend allowance as the material has to stretch more to accommodate the bend. Conversely, a smaller bend radius necessitates a smaller bend allowance.

Thickness of the Sheet Metal

The thickness of the sheet metal also influences the bend allowance. Thicker materials require a larger bend allowance to avoid excessive thinning or cracking during bending. Thin materials, on the other hand, can tolerate a smaller bend allowance without compromising the structural integrity of the bend.


Springback is the elastic recovery of the sheet metal after bending. When the press brake is released, the material tends to spring back slightly, reducing the actual bend angle. To compensate for springback, an additional bend allowance is required. The amount of springback varies depending on the material properties and the bending process.

Determination of Bend Allowance

Based on the aforementioned factors, the bend allowance can be calculated using the following formula:

Bend Allowance = (Bend Radius + Material Thickness) x Springback Factor

The springback factor is a material-dependent constant that can be obtained from tables or experimental data. It typically ranges from 0.01 to 0.05 inches per foot.

For instance, consider bending a 0.062-inch thick aluminum sheet metal with a bend radius of 0.25 inches. Assuming a springback factor of 0.02 inches per foot, the bend allowance would be:

Bend Allowance = (0.25 + 0.062) x 0.02 = 0.0062 inches


Determining the correct bend allowance for a sheet metal press brake is essential for achieving precise and accurate bends. By considering the material properties, bend radius, sheet metal thickness, and springback, you can calculate the appropriate bend allowance and ensure the desired bending results. Understanding these factors and applying them effectively will enhance the quality and efficiency of your sheet metal fabrication processes.


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