What is a mandrel bend?

A mandrel bend is simply a bend that maintains a consistent diameter throughout the bend. Mandrel bending is used where the inside radius of the tube must be bent without wrinkling or deformation. This is achieved by inserting a flexible or solid fixed "mandrel" to support the interior walls of a tube during the bending process. The walls are supported internally with either a flexible mandrel that bends with the tube, or a fixed "bullet" mandrel set internally at the pivot point of the radius die. Mandrel bends are commonly used in the manufacture of automobile exhaust pipes, turbocharger intake and outlet tubing, and custom exhaust systems.

              Crush Bend                                                 Mandrel Bend 

Why Are Using Mandrel Bends So Important?

Imagine a plastic straw that get from any fast food restaurant. If the straw is completely straight, it's very easy to blow air through it because there are virtually no restrictions. Now you bend the straw 90 degrees into an "L" shape blowing air through the straw will become much more difficult, as the internal diameter at the straw's elbow will have changed from a circle to a narrow slit.

This is exactly how the piping in your vehicles intake, intercooler and exhaust systems work. Air is traveling through pipes that when crush bent become very restrictive to the flow of air. Mandrel bending works much like the flexible straws that you can buy in a grocery store. When the straw is bent, a flexible section of the straw expands to maintain the round opening no matter how much of an angle the straw is bent at. When an exhaust or downpipe is manufactured with mandrel bends, the steel is allowed to stretch on the outside of the bend and compress on the inside of the bend, maintaining the nominal pipe diameter. This helps to eliminate backpressure while maintaining exhaust gas velocity.

Where Should Mandrel Bends Be Used?

Mandrel bends are most commonly used in any application that maximum flow is critical to performance. In the automotive world they are used in high performance exhaust systems, intakes and intercooler piping. Both mild steel and stainless steel mandrel bends are used when custom building an exhaust system. Stainless steel offers a much higher level of durability and corrosion protection and is the most commonly used material for high performance exhaust.

When building both intake and intercooler piping systems aluminum is usually the material of choice. Aluminum mandrel bends are relatively inexpensive and offer superior heat dissipation properties along with immense weight savings over steel.

What To Watch Out For When Buying Mandrel Bends

The quality of the materials used to make mandrel bends varies a great deal. While searching for bends to use on your next project be sure to use the highest quality available. Often the cheaper bends found on eBay and similar places use the absolute lowest quality aluminum and steels possible. While they may be a bit easier on the wallet they can present some fabrication challenges, the most common being weldability. There is nothing worse than trying to lay down beads you can be proud of when working with contaminated materials. Also avoid polished bends whenever possible, a raw or machined surface is much easier to work with.

If your searching for mild steel mandrel bends and you plan on Tig welding them avoid aluminized bends at all costs. The aluminized material gives off toxic fumes that can cause some health issues especially after prolonged exposure.

We Offer A Large Variety Of Ultra High Quality Mandrel Bends 

Aluminum Bends

Mild Steel Bends

Stainless Steel Bends