How to expand square tubing

Multiform Tubes is an expert at tube manipulation and can offer various solutions to suit any need. The specific services we provide are very broad, including bending, expansion, reduction, and drilling. We also work with various shapes, lengths, and wall thicknesses. Our skills are impressive and we can offer lots of advice too. This includes answering questions like how to expand square tubing.

Why expand?

There are many reasons for expanding tubes, regardless of the shape. It may be that the tubing needs to slot together as part of a system to convey fluid or gas. It may even be part of a product like a handrail. The expansion could even be to allow the tube to fit to a specific fixture or to create a tight joint.

The challenge with square tubing

How to expand square tubingIt is harder to expand the inner diameter of a square tube. There are a number of unique challenges here that you need to think about. One is the wall thickness and how vital it is to maintain a tight tolerance.

The biggest challenge with square tubing is because of the welded seam. This is generally hidden in a corner where it is not clearly visible. The issue is that the seam will have different characteristics to the rest of the tube. For example there will be differences in springback, hardness and flow. As a result one side will have a higher resistance to the forming forces and it can result in an uneven expansion. It is vital that the manufacturer considers this.

The expansion

In terms of how to expand square tubing, there are two options just like with expanding round tube.


The first is to use a static die. This process is also commonly known as inline forming. It involves creating a die that can be inserted into the end of the tube and hammered in to expand the diameter.

This conventional approach to expanding square tube can be very effective and produce good results. There are some drawbacks though. Firstly each die is a specific size to suit the job so the tooling time is longer. The die also determines the length of the end form. There is no way to adjust it once the die is made other than making a new one.


The second type of expansion is to use a segmented die. Unlike static ones, these dies have segments that can move. The manufacturer will insert it into the end of the tube and then let it expand to the right size. The die then collapses a small amount so it is easy to remove from the tube.

This is a very flexible approach and can create more complex profiles. In addition there is a smaller contact area with the tubing. As a result it can provide a more accurate expansion.

There are some drawbacks with this method too though. First off there are some limitations on the amount of expansion that is possible. For example the segments can only open so far and generate so much force. There may also be some tool marks.

Expert services

The above should give you more information about how to expand square tubing. If this is a service you need it is wise to choose a professional like us. We will ensure the expansion is precise to suit your needs. Simply contact Multiform Tubes to talk about services.