# Similarities Between Bending Round and Rectangular Tubing

Bending square and rectangular tubing is more difficult than bending round tubing and pipe.

Maybe you would like to check out our Square Tubing Bending Machine or Pipe Rolling Machine page.

Square and rectangular tube bending, though a common practice, is wrought with many challenges. The hollow structure of a tube makes it more likely to fall victim to distortion problems such as growth, shrinkage, concavity, and oil canning. And bending square and rectangular tubing is more difficult than bending round tubing and pipe. Round tubing and pipe can be more easily and more fully encapsulated within the bending dies than square and rectangular tubing. This is true whether the bending is done on rotary-draw benders, three-roll benders, or ram benders.

When the curved parts are to be used in construction, it is imperative that the steel fabricator and the bender/roller communicate exactly how the parts are to be oriented. Are the square tubes rolled against one of the sides or off-axis? Are the rectangular tubes rolled against the strong axis or the weak axis? Or are they to be rolled off-axis? Equally important is whether or not these curved tubes are architecturally exposed (AESS).

## Similarities Between Bending Round And Rectangular Tubing

- Bending Techniques: Both round and rectangular tubing can be bent using similar techniques, such as mandrel bending, press bending, or rotary draw bending.
- Material Considerations: The material properties and characteristics of the tubing, such as strength, ductility, and elasticity, influence the bending process similarly for both round and rectangular tubing.
- Bending Parameters: Factors such as bending radius, degree of bend, and tangent lengths are important considerations in both round and rectangular tubing bending processes.
- Precision Requirements: Achieving precise bends with consistent dimensions and tolerances is critical for both round and rectangular tubing to ensure proper fitment and structural integrity.
- Applications: Round and rectangular tubing are used in similar applications across various industries, including construction, automotive, aerospace, and manufacturing, where they serve as structural components, support elements, or aesthetic features.
- Bending Challenges: Both types of tubing may encounter similar challenges during the bending process, such as distortion, wrinkling, or springback, requiring careful consideration and mitigation strategies.

The basics of bending are the same for all material in that certain information is required to produce an accurate part :

- Degree of bend
- Radius of the bent section
- Chord of the bent section
- Arc length
- Slope of the bent section
- Tangent lengths

### Degree of bend

When bending round tubing, the degree of bend is typically specified by the angle through which the tube is bent from its original straight form. This angle is measured in degrees and can vary depending on the application requirements. For rectangular tubing, the degree of bend refers to the angle of deflection from the original straight orientation of the tubing. Achieving precise angles is crucial for ensuring structural integrity and fitment in various projects such as construction, automotive, and manufacturing. Factors influencing the degree of bend include the material properties of the tubing, its thickness, and the bending method used (e.g., mandrel bending, press bending). Careful consideration of these factors is essential to achieve the desired degree of bend without compromising the tubing’s integrity or dimensional accuracy.

### Radius of the bent section

The radius of the bent section in round and rectangular tubing bending refers to the curvature of the bend. For round tubing, the radius is typically specified as the distance from the centerline of the bend to the inner surface of the tubing. In rectangular tubing, it refers to the radius of the curve along the inner or outer wall of the bend.

The radius of the bent section is a critical parameter affecting the appearance, structural integrity, and functionality of the bent tubing. It determines the smoothness of the bend and influences factors such as stress concentration and material deformation during bending.

Achieving the desired radius requires careful consideration of various factors, including the tubing material, thickness, and bending method. Mandrel bending, for instance, often produces tighter radii compared to other bending techniques. It’s essential to select the appropriate radius to meet design requirements while ensuring that the tubing retains its structural strength and dimensional accuracy.

### Chord of the bent section

The chord of the bent section in round and rectangular tubing bending refers to the straight line segment connecting the endpoints of the curved section. In other words, it is the shortest distance between the two points on the outer surface of the tubing where the bend begins and ends.

The chord length is a crucial parameter in tubing bending as it affects the overall length and fitment of the bent tubing within a given space or assembly. It directly influences the clearance requirements, mating interfaces, and overall aesthetics of the bent component.

Achieving the desired chord length involves careful consideration of factors such as the bending radius, tubing diameter or width, and the degree of bend. Precision in determining the chord length is essential for ensuring proper fitment and alignment in various applications, including structural frameworks, handrails, and architectural elements. It’s vital to accurately measure and control the chord length during the bending process to meet design specifications and functional requirements.

### Arc length

The arc length in bending round and rectangular tubing refers to the length of the curved section along its outer surface. It is the distance measured along the outer circumference of the bend between the two endpoints of the curved section.

The arc length is a critical parameter in tubing bending as it directly affects the overall length and fitment of the bent tubing within a specific assembly or application. It influences factors such as clearance requirements, mating interfaces, and overall aesthetics.

Achieving the desired arc length requires precise control over the bending process, including factors such as bending radius, tubing diameter or width, and the degree of bend. Careful consideration of these factors ensures that the bent tubing conforms to design specifications and functional requirements.

Accurate measurement and control of the arc length are essential to ensure proper fitment and alignment in various applications, including structural frameworks, handrails, and architectural elements. It’s vital to calculate and verify the arc length during the bending process to achieve desired outcomes.

### Slope of the bent section

The slope of the bent section in bending round and rectangular tubing refers to the rate of change in elevation along the curved portion of the tubing. It represents the angle of inclination or declination of the bent section relative to its original orientation.

The slope is a critical parameter in tubing bending as it influences factors such as drainage, aesthetics, and structural integrity. A consistent slope ensures proper drainage of fluids in plumbing applications and enhances the visual appeal of architectural elements.

Achieving the desired slope requires precise control over the bending process, including factors such as bending radius, tubing diameter or width, and the degree of bend. Careful consideration of these factors ensures that the bent tubing conforms to design specifications and functional requirements.

Accurate measurement and control of the slope are essential to ensure proper fitment and alignment in various applications, including plumbing systems, handrails, and structural frameworks. It’s vital to calculate and verify the slope during the bending process to achieve the desired outcomes and ensure optimal performance of the bent tubing.

### Tangent lengths

In bending round and rectangular tubing, tangent lengths refer to the straight sections of tubing on either side of the curved portion. These lengths connect the endpoints of the curve to the unaltered sections of the tubing.

Tangent lengths are crucial for ensuring proper fitment, alignment, and structural integrity in various applications. They determine the transition between the straight and curved sections of the tubing, influencing factors such as clearance requirements, mating interfaces, and overall aesthetics.

Achieving the desired tangent lengths requires precise control over the bending process, including factors such as bending radius, tubing diameter or width, and the degree of bend. Careful consideration of these factors ensures that the tangent lengths meet design specifications and functional requirements.

Accurate measurement and control of tangent lengths are essential to ensure proper fitment and alignment in applications such as architectural elements, structural frameworks, and handrails. It’s vital to calculate and verify tangent lengths during the bending process to achieve the desired outcomes and ensure optimal performance of the bent tubing.

It isn’t necessary to know all six parameters. However, at least three must be known to produce a bent section.

## Top 5 Methods for Bending Round and Rectangular Tubing

After the information is collected and analyzed, the appropriate method of bending is chosen. Bending methods are the same for round, square, and rectangular material:

- Rotary draw bending
- Induction bending
- Roll bending
- Increment bending
- Compression bending

**Here You should also check out our Profile Bending Process page.**

As with all bent parts, the customer’s tolerances and appearance requirements help determine the proper method.

Preventative measures that can be taken include increasing the wall thickness of the tube to help reduce or totally eliminate the risk of oil canning and concavity. In doing so you would need to take into consideration the increased weight, and how it affects your application.

It is equally important to convey expectations when the curved pipe or tubing is to be used as component parts of machinery and equipment. For example, some original equipment manufacturers (OEMs) actually prefer to have concavity on the inside radius of the bent part: a design that actually makes the steel section stronger in this application.

By communicating this information and conveying expectations clearly, many problems can be prevented. And solutions to expected problems can be resolved ahead of time making the process timelier, less frustrating, and more cost effective.

Related Reading: https://www.thefabricator.com/tubepipejournal/article/tubepipefabrication/bending-square-and-rectangular-tubing