A Crash Course on the Press Brake: Three Styles of Metal Bending

large steel tubes fabricated on press brake.

If you’re not immersed in the metal fabrication business day-in and day-out, you may get a little overwhelmed by the amount of terminology that you’re hearing and reading about from the fabricator. How are you supposed to know the difference between all of those machines? Isn’t a bend just a bend? The truth is, “No,” not every bend is exactly the same. The reason why is because there are different methods available for creating those bends, and not every metal responds to bending in an identical manner. That’s why it’s important to make sure the machine operators have the years of experience, training, and know-how needed to effectively run the press brake while keeping mistakes at a minimum at best.

When it comes to explaining sheet metal bending, we’d like to help you expand your knowledge of the metal bending business. To get you on your way, here is a breakdown of the three most common forms of bending on the market today: Coining, air bending, and bottom bending.


Coining is one of the most popular bending methods used in metal fabrication today. Operators use a press brake that features a punch and die to form the metal into specific angles. In this process, the sheet or plate lays down flat on top of a die. The metal is then compressed between the punch and die with an extreme amount of tonnage to create a precise bend angle in the metal. The die can be formed to have a wide variety of shapes or angles falling in the categories of obtuse, acute, and right angles; the bend options aren’t heavily restricted. But no matter what type of angle is used with the die, the sheet metal will bend precisely to that angle. Coining allows for a precise, consistent bend every time.

Air Bending

Another common form of bending, air bending is accomplished in a slightly different fashion when compared to coining. When air bending is used to form metal, the ends of the metal plate or sheet rest on the die shoulders while the central portion of metal is unsupported by a die geometry. This is the portion of the metal sheet that is bent using the downward force of a punch. In coining, the angles of the punch and die determine the angle of the bend in the metal sheet. However, in air bending, the bend angle is determined by how far down vertically the punch presses into the die. It is important to note that, when air bending is used, there is the potential for springback to occur. Therefore, machine operators must make the necessary calculation adjustments to the bend angle to account for this movement.

Bottom Bending

The final category of sheet metal bending is known as bottom bending or “bottoming.” In this method, the metal sheet or plate lays flat while the top punch and die are brought together above and below the work using minimal tonnage. In bottom bending, the punch and die never make full contact with the metal sheet. This creates a bend that is liable to spring back inward toward its original shape. To compensate for this, tooling must be used to create a slightly more acute angle than what is normally requested in the job specs. Once the sheet metal is released, it’ll naturally move back out a bit into the desired bend angle. Different materials and their thicknesses at the time of the bend will respond differently to springback, so it’s important that the machine operator fully understand the unique properties of each metal used. Bottom bending can be risky, however, because airbending allows you to deviate from the rigid V-die opening. Some tooling manufacturers don’t recommend bottom bending because of the liabilities and risks that exist with the process. However, many fabricators understand the value and the need for bottom bending and employee highly knowledgeable operators to handle the machines with ease.

At Swanton Welding, we take pride in the work we’ve done, producing exceptional steel products for customers across the nation. We stand proud of the work we do, work that exceeds the level of service from most of our competitors. It is our purpose to supply our customers with the best service possible to meet their needs and budgets. How can we help you discover the possibilities that await when you say “Yes” to Swanton Welding? Call 419-826-4816 for more information.

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