How To Bend Roll Bar Tubing [DIY Complete Guide]

When it comes to bending roll bar tubing, many people consider it to be an art form. However, for keen enthusiasts, it’s possible to not only learn the skill at home but also to master it themselves as long as they’re prepared to dedicate the energy and time to it.

Why would you need to know how to bend roll bar tubing?

Well, if you’ve ever wanted to build tube bumpers or a roll cage for yourself then you’ve probably wanted to be initiated into this dark art.

Here, we’ll look at the different equipment and tools that you’ll need, the best ways of using them and understanding the right bends for your particular project.

 

Bending – The Basics

When you’re ready to bend roll bar tubing, you first need to know the properties of the pipe or tube that you’re going to be working with.

Pipe that is used to transport air or fluid will normally be specified by its pipe size, however when it comes to using a bending machine, you’ll need to know the pipe’s key variables including its wall thickness, centerline radius and outside diameter.

One thing that you’ll need to bear in mind is that the wall thickness between pipes can vary, and this variation must therefore be accounted for, particularly when using a bending process that requires tight-fitting, precise tooling on a small bend radius.

As with any project having the right tools makes the job easier so here are our choices of the 5 best tube benders for a roll cage…

The Bending Variables

The bending variables you need to know include:

• The inside bend radius
• The outside bend radius
• The centerline or neutral line
• The distance between bends
• The bend angle

Springback

One thing to be aware of when bending roll bar tubing is that tubes will experience springback once they’ve been bent, and this produces bends which goes through radial growth.

The smaller the centerline radius of the bend and the harder the tube, the more springback and radial growth there will be.

It’s also worth noting that steel undergoes more radial growth than copper, but stainless steel goes through the most of all.

Longitudinal Weld

While some tubes are seamless, the majority are made using a longitudinal weld.

The consistency, size and quality of the weld seam is very important in tube bending as if the joint’s two edges don’t perfectly align or if the bead is inconsistent or too large, the tube will not be perfectly round and this is a problem when creating a perfect bend.

Elongation

Elongation also occurs when you bend roll bar tubing, with stretching of the outside radius. The bend’s outer surface will cave in, resulting in the cross section being distorted from its round shape.

Although ovality works in some applications, if you’re doing precision work it is unacceptable.

Tube Bending Process

There are four types of tube bending process:

• Ram type bending
• Compression bending
• Roll bending
• Rotary draw bending

Ram-type Bending

Ram style benders can be found in most muffler shops and this is a simple and old-fashioned method of tube bending.

Using a ram which is hydraulically driven, a tube is forced against pivot blocks or rollers. This method allows you to achieve a CLR (centerline radius) 3-4 times the outside diameter of the workpiece.

In this method, the inner diameter of the workpiece isn’t supported with a lot of stretching on the outer side of the tube’s bend.

Ram type bending is ideal for square tube applications and is the most affordable way of bending roll bar tubing but since it isn’t easy to control it isn’t suitable of cosmetics matter.

Roll Bending

The method of choice for large construction workpieces, this method involves 3 rolls which are in a pyramid construction, either horizontally or vertically.

These rolls then move producing specific radii. Alternatively, a pinch style 2 roll bender can be used for this method. Roll bending can be used for producing spirals.

Compression Bending

This method uses a compression die or roller to bend your workpiece round the stationary bend die to compress the tube.

Suitable for symmetrical workpieces, this method works best for those tubes which will be bent to a centerline radius which is a minimum of 3 times the outer diameter of the tube.

It isn’t suitable for workpieces that have a CLR which is under 3 times the diameter of the tube.

Perfect for commercial and household products, the most common use for compression bending is to make items like towel rails.

Rotary Draw Bending

Rotary draw bending is perfect for precision tasks and for applications which involve tight radii since it allows for maximum control.

Good Tooling Techniques

If you want to get the perfect bend, you’ll require an excellent tooling set up, especially when using the rotary draw method.

The hardness of the mandrel is vital – if you’re bending a hard tube you need a softer mandrel and vice versa for the best result. Tooling also needs to take the radial growth into account.

Excessive radial growth will result in a noticeably different radius at the start of the bend.

A smaller radius bend die will often be required. Good welds are also important, especially when rotary draw bending. Inconsistency in the bead affects the wiper die, pressure die and mandrel.

The position of the wiper die is also critical – angling it slightly is important so its end can make contact with the tube before the tangent point of the inside radius.

The wiper due must also be in good condition and sharp.

When it comes to the clamping die, you need to note that it should be 3 times longer than the diameter of the tube. This ensures that the pressure is spread properly over a larger area.

If you’re working on a piece that has a short distance between its bends, this can be challenging however if you use special tooling you can deal with this easily.

A multi-stacked arrangement can resolve the problem. Some tube types also require a set of flexible balls to the end of the mandrel and this must be position properly when the machine is set up.