Introduction to Square Tube Bending Machine

Posted on Aug 30, 2021

Square Tube Bending Machine

A square tube bending machine is a bending tool used to bend rectangular tubes and pipes. Visit IMTS to learn more about this bender tool.

What is a Square Tube Bending Machine?

Bending round or square tubes and pipes requires a square tube bending machine. A wide range of pipes can be bent on a bender. Square, rectangular, or round tubes can be bent. The good news is that tube benders are easy to set up. While round tube tools are standard tools, bending square tubes requires special tools that fit the tube’s cross-section. In this article, we will address different aspects of the square tube bending machines.

Bending Process Explained

A standard pipe bender can bend pipes with thin walls and small radii (using an air cylinder). The tube bender has more uses than the benders that use air cylinders. The bending process relies heavily on modern science and technology. Bending dies are designed with specific curve angles and the square tube bending machines are computer-controlled. Stress and strains can be accurately predicted by mathematics.

However, the rules are not just about modern gadgets and sophisticated mathematics. The basic concepts of pipe bending are the same as those used by blacksmiths for centuries, developed long before the slide rule, calculator, or desktop computer. While the bending procedures for round, rectangular and square materials are the same, square and rectangular tubes require special consideration.


The bending basics are the same for all materials. The parameters required to produce an accurate part include the degree of bending, radius, chord, arc length, slope, and tangent length. After collecting and analyzing the information, the appropriate bending method is selected. The bending methods include rotary bending, induction bending, roll bending, incremental bending, and compression bending. They all apply for round, square, and rectangular materials. The tolerances and customer appearance requirements help determine the method.

Square and Round Corners
The corner radii determine whether the mandrel will correctly fit the inside diameter (ID) of the pipe. In some cases, workpieces with rounded corners tend to roll away from the bend radii, causing the material to twist.

Size, Wall Thickness, and Radius
The thicker the wall, the tighter it can be formed with minimal deformation. Forming 8 by 8 inches. steel pipe up to a 5 ft radius will cause greater distortion if the wall thickness is 0.188 inches than if the wall is 0.500 inches. Design parameters and the required appearance of the final product often help in choosing the thickness.

Architecturally Exposed Section Material (AES) requires a more detailed analysis of bend radius, wall thickness, and bend method. In addition, if minimal deformation in a bent section is allowed, the operator must pay more attention to proper bending procedures.


Multiple tips can make it easier to bend square and rectangular materials and reduce the amount of distortion in the bent sections. The factors include wall thickness, material, the OD (outer diameter), and the ID (inner diameter) of the material. A thicker wall allows a smaller bend radius and greater material extensibility with less deformation. The higher the ductility and malleability of the material, the larger the radius.

Welding Seam
The ideal position of the welding seam is in the center of one of the four sides. The closer the weld seam is to the rounded corner, the greater the chance that the mandrel will not fit properly and the weld will crack. If possible, the weld seam should be placed on the neutral axis of the bent section.

:: Read More: The Awesome CNC Tube Bending Machine


Square tube bending machines are versatile and have a number of applications. Let us delay no further and take a look at the common applications of the benders.

Square/rectangular Tubes

As the name suggests, the primary application of a square tube bending machine is to undertake rectangular and square tube bending. Bending rectangular or square tubes can be done with a special tool. During this process, the pipe is slightly compressed inside to allow the material to flow. This tube bending procedure is very economical and faster than a mandrel bender.

When a rectangular tube is bent, the material often exhibits less distortion when hard bent. For easy bend, the greater the difference between the sides of the tube (e.g., a 16 by 4-inch section has a greater difference than a 12 by 4-inch section), the greater the deformation or concavity on the bend ID. Concavity is less of a problem with thick-walled materials.

:: Read More: These Benefits Make a CNC Tube Bender a Great Machine

Gas/water Pipes

For bending gas and water pipes, they can be bent on a square tube bending machine using standard pipe bending tools. A separate bend segment is used for each pipe size. Along with pipes that meet DIN EN and other standards, the balustrade pipes can also be bent without a mandrel. These pipes have a larger bend radius. It is not possible to bend stainless pipes. Such pipes should always be bent with a mandrel bender. Bending gas pipes with a standard bender is faster than with a mandrel bender.

Pipes can be flattened in a metal or steel structure. Struts can be made of flat tubes, for example. For bending heavy pipes with large diameters up to 400 mm, 3-roll benders for a larger diameter range are very expensive or even not produced by 3-roll bender manufacturers. If the bend radius does not need to be too small, the pipe can also be bent step by step with a bending press.

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