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Bending Flat Bar

Flat Bar Bending Machine

Here for everything you need to know about flat bar bending with BIT. BIT is proud to recommend the PBH Section Bending Machine for your flat bar rolling project.
You should also check out our Profile Bending Process page.


Flat Bar Bending/Metal Flange Roll Forming
BIT PBH Flat Bar Bending Machine has a super-strong ability to bend flat bars and high precision. Therefore, a flat bar bender is often used to bend bar steel and make flanges in practical applications, we also call the profile bending machine the flange forming machine.
At the same time, the BIT PBA Series Aluminum Bending Machine can perfectly bend aluminum flat bars.

PBH Flat Bar Bending Machine

Flat bar bending machines are an integral part of BIT’s comprehensive portfolio, leveraging four decades of innovation and expertise in bending and rolling machinery. These section bending machines specialize in the transformative process of shaping flat bar stock into precisely curved components, offering several advantages over traditional cutting methods like laser or plasma burning.

flat bar bending machine
Flat bar bending machine

Bar rolling demonstrates a remarkable advantage in material efficiency by minimizing scrap during the production of flat rings and ring segments. Compared to cutting from sheets, this technique conserves material, saves time, and reduces overall expenses. The accuracy achieved with rolled bars matches the stringent requirements of various manufacturing methods.

BIT’s array of flat bar rolling and bending machines caters to diverse customer needs, ensuring optimal equipment selection and tooling dies for specific bar rolling applications. These machines, equipped with cutting-edge technology, minimize distortion, a common issue in bending processes, ensuring high precision while bending large flat bars. This precision translates to reduced material wastage, minimizing trimming requirements, and effectively cutting down on costs.

Our PBH profile bending machine‘s capabilities extend to rolling flat bars both “the easy way” (perpendicular to the bar’s largest dimension) and “the hard way” (parallel to the largest dimension), maintaining tight tolerances in all directions. Additionally, BIT’s flat bar rolling machines can handle multiple bends or variable radii, offering versatility to accommodate diverse project requirements.

By leveraging state-of-the-art equipment and expertise, BIT ensures the delivery of high-precision, distortion-free, and cost-effective solutions for flat bar rolling applications. This technology allows us to meet various customer demands while optimizing material usage, precision, and production efficiency.

Flange Rolling Machine

Many Chinese customers refer to the hydraulic flat bar rolling machine as a flange bending machine. BIT is just an ordinary profile bending machine for bending flat steel.

A flat bar bending machine is a specialized piece of profile bending machine(also called a section bending machine or angle roller) used in metal fabrication to bend flat bars of various sizes and thicknesses. The PBH flat bar bending machine/profile bending machine works by applying pressure to the flat bar with a series of rollers, gradually bending the bar into the desired shape.

Works Principle

The principle behind the operation of the PBH flat bar bending machine is based on the plastic deformation of metals. When a flat bar is placed between the rollers, the pressure applied to the bar causes it to deform and bend. The rollers or dies can be adjusted to control the amount of pressure and the angle of the bend, allowing for precise and repeatable bends.


Applications of bent flat bar are numerous and varied across a wide range of industries. In construction, bent flat bars are commonly used for reinforcing concrete structures, such as beams, columns, and walls. Bent flat bars are also used in the fabrication of metal furniture, railings, and ornamental fixtures. The automotive industry uses bent flat bars for chassis and body components, while the aerospace industry uses them in aircraft frames and landing gear.

Bent flat bars are also used in industrial machinery and equipment, such as conveyors, cranes, and lifts. They are often used in the production of agricultural equipment, such as plows and cultivators. Bent flat bars can be found in many household items, such as gates, fences, and shelving.

PBH 200 Flat Bar Bending Machine
PBH300 Flat Bar Bending Machine/Hard Way X-X Axis
PBH 450 Flat Bar Bending Machine/Easy Way Y-Y Axis

Bending Capacity of PBH Flat Bar Bending Machine

Hard Way X-X AxisEasy Way Y-Y Axis
ModelSpecification (mm)Min Inside Dia (mm)Specification (mm)Min Inside Dia (mm)
PBH-12080× 10800180× 20500
PBH-140100× 25700200× 35600
PBH-200120× 251000250× 301000
PBH-300150× 301500250× 401000
PBH-360175× 401500350× 50900
PBH-450200× 502500400× 602000
PBH500250× 703500450× 701000
PBH-550250× 703500500× 801200
PBH-600300× 704000500× 1001600
PBH-700300× 805000650× 1002000

Hydraulic bar bending machine

Six Steps Of Flat Bar Bending

  • Steps 1#: Loading bending steel bar – the steel bar is inserted in between the top roller and the right lower roller. The steel bar can be supported if necessary and is not subject to deformation stress.
  • Steps 2#: The right lower roller up to the top roller movement achieves the pinching position – the steel bar is blocked in between the rolls and can be moved forward and backward rotating the rolls. The pressure exercised is lower than the one necessary to deform the profile.
  • Steps 3#: Pre-bending between the top roller and the left roller – the right roller slowly rises, starts rolling, and performs pre-bending between the top roller and the left roller.
  • Steps 4#: Working phase – in this phase the pressure increases and the deformation of the profile takes place, by translation of the profile and movement of the rolls.
  • Steps 5#: Pre-bending between the top roller and the right roller – The left roller is down and the right roller is raised. The steel bar is sent to the left and the three rolls begin rolling, pre-bending between the top roller and the right roller.
  • Steps 6#: Unloading of the steel bar – the pressure on the profile is eliminated and is increased the space between the rollers so that the steel bar can be extracted from the machine.

How to bend a radius in flat bar

Bent flat bars are frequently used in tank stiffeners, matching flanges, curved lintels, hand rails, curved stringers, pipe clamps and kick rails on circular platforms.

2 methods flow of roll bending flat bar

Bars can be bent with virtually every bending process. For very tight radius bending you can utilize a draw bending process where you must be pull the material (draw the material) around a bend die matching the desired bend radius. But for larger or sweeping radii must be utilize a roll bending process (section bending). At this time, need to use flat bar bending machine.

Flat bars are solid, which means that they can be easily bent into the shapes required by a project. There are two ways to bend non-circular or non-square bars:

bend flat bar
2 methods flow of roll bending flat bar
  • Easy Way : The Easy Way: This involves bending a bar along the wider axis of the bar. This means an easier bend, reducing the problem of rippling on the inside of the curve. Bars bent the easy way resemble a belt when completed.
  • Hard Way: The Hard Way: Bars bent in this manner are bent along the thicker axis. This also presents more difficulty during the bending process, as rippling and compression can occur on the inside of the bends. When bent the hard way, bars resemble a metal washer.

Minimum Bending Radius When Bending Bars

There is not a mathematical formula for determining the minimum bending radius of steel sections. To better explain this, lets look at bar bending. Steel is curved using a cold-roll bending process. Steel sections are put into a flat bar bending machine (also called “section bending machine” or “angle roll”) with a three or four roll configuration. Rollers put force against the feed path to force the metal stock into a predetermined curved path. There is force applied by the rolling machine (stress) which in turn changes the structural steel into a curved shape (strain).

Flange forming
Hard way to roll bend flat bar
Flange Bending Machine
flat bar bending machine

How to bend metal bar use PBH flat bar bender

The flat bending of a flat steel bar and the bending of square steel bar can choose any combination of angle rolls molds. Read More: Profile Bending Machine Operation Manual (2)

The steel bar’s section rolling process uses an asymmetrical bending, put the 3D guide rolls are raised slowly in the roll bending process, otherwise the material would be distorted. Before the roll bending procces, must be adjust the guide roller to the same distance, and the steel bar has the correct angle relative to the roller axis, which is suitable for bending small workpieces with small bending stress, which will cause slippage during the bending process. Mainly due to the low friction during feeding, increasing the roller clamping force can eliminate slippage. The steel bar can be bent into a circular workpiece with a diameter slightly larger than the die diameter, and the friction clutch should be adjusted tighter.

Minimum Bending Radius Illustration

Elastic state

If you look at the diagram left, steel is very ductile, and after a very brief elastic state the material goes into plastic deformation. The goal is to reach the desired radius without reaching the necking or ultimately the fracture point

Looking back at the diagram left, the goal is to maximize the elongation limit in the bar bending process which is done by going with steel that is more ductile.

Three minutes to read


  • Metal flat bars or ‘Flat Sections’
  • Steel flat bars are one of the most basic of building materials.
  • Flat metal bars are practical anywhere a connection between two beams is required.

Appliction of flat bars

  • Base plates
  • End plates
  • Stiffeners (secondary plates)
  • Tabs
  • Gussets
  • Splice plates

When a flat section is cut into smaller pieces it is called a flat steel plate. Flat sections are often used to strengthen other beams and are sometimes used to reinforce timber joists. That is why it is so typical to see a flat steel bar with holes in it, ready to be bolted in place.

What is “Roll Forming?”

The term “roll forming” lends itself to great ambiguity.

roll forming

Since steel mills producing “long sections” of structural steel–including angles, bars, beams, channels, and tees–manufacture their products through a rolling process, these sections are often referred to as, for example, “rolled beams.” (In part to distinguish them from built-up girders, i.e. beams made by welding three pieces together.)

roll bending

And these straight sections are often curved to a given radius, in a prescribed orientation, through a given number of degrees or a given arc length to be used in a variety of applications. Since the most common way of curving structural steel involves three-roll benders (also called “angle rolls,” “section benders,” and “pyramid rolls”) bending with these machines could also be called “roll forming.”

In construction, curved steel beams, for example, are often used as roof supports, canopies, and bridges; in manufacturing, curved steel sections are used in tractors, antennas, rail cars, and tanks–to name just a few applications.

But perhaps the most common use of the term “roll forming” refers to a process whereby a strip of sheet metal or relatively light plate is fed off a coil into a series of rollers which progressively form the desired shape. The method has been used to form residential gutters whose length is limited only by the length of the metal in the steel or aluminum coil. The gutters can be formed to length in a truck at the job site. This type of roll forming is most commonly used to produce many feet of a formed product whether that be angles, channels, tees, etc.

Four basic knowledge of flat steel

Flat bar sizes

Flat bar sizes are generally available and extruded shapes of the most common sizes of angles, tees and I-Beams can be found. In the world of specialty alloys, however, the demand for such products is so small that structural shapes are rarely produced for standard inventory.

Flat bar formed by cutting

Limited quantities of flat or square bar are produced in several alloys where they are in demand for aerospace applications or where cutting from plate is prohibited. This includes titanium alloys and PH 15-5.
However, for most other stainless and nickel alloy grades, flat bar is produced only when there is a significant quantity to justify a mill production run. This usually means a minimum of 2500# per size.

Fortunately, most flat bar needs can be accommodated by cutting flat bar from plate. Metallurgically speaking, this poses no problem because stainless and nickel alloy plate properties are nearly isotopic. Transverse mechanical properties can be slightly below those in the longitudinal direction, but the minimum tensile properties established for each plate material are tested in the transverse direction anyway.

Dimensional tolerance

The primary difference between a true flat bar and a flat bar cut from the plate is dimensional tolerance. In the true flat bar, tolerances for width and thickness are restrictive and more or less mirror those established for the round bar.
In cutting the bar from the plate, the width tolerance will be more generous and in line with the cutting method. Typically the permitted range of variation in width is 1/8”.
The thickness of the flat bar cut from the plate will be the same as that of the plate. Plate thickness tolerances are skewed to the heavy side. The minimum under tolerance for plate thickness is 0.010”, while the over tolerance is either unrestricted or is at least 0.090” and increases with thickness.

Edge and corner conditions

Finally, edge and corner conditions will likely be different. For a true bar, the surface finish on all four sides will be more or less the same. Corners will be full and nearly sharp with only a slight break. They will be nearly free of twist and camber. On a flat bar cut from plate, the surface finish on the sides that were cut will differ from the top and bottom, which are the original plate surfaces. If the bars are merely stripped from plate, they may show some twist or camber. This can vary greatly with the cutting method.

More bending methods for metal profiles

Reference Reading: Best Beginner’s Guide to Metal Profile Bending