A Complete Guide To Pipe Bending Mandrels

tube bending mandrel

Precision is an absolute factor for any kind of bending operation. A perfectly bent tube can enhance the performance and durability of any equipment it is used in. 

Sometimes, a tube may endure bending damages and errors including wrinkles and collapses. Tubes with a tight radius, thin internal walls, and harder to bend material are prone to these errors. Wrinkled tubes can decrease the overall lifespan of the tube.

To prevent these errors and achieve exceptional bends you must use a mandrel. It is a steel rod inserted in the tube avoiding it from collapsing during the bending process. This technique perfects the tube bend without wrinkling or breaking it at the bending point.

A mandrel is a tooling component that is used during a pipe bending operation to boost its accuracy to offer incomparable performance. It is designed to tackle many bending issues, including errors and damages caused during the tube fabricating process. 

Tube flattening, wrinkling, kinking, and collapsing are caused by when a high pressure to bend the tube is exerted. They can drop the quality of bends and the functionality of the equipment in which such damaged pipes would be used. They can also cause fatigue in metal, steel, and even plastic pipes. 

Mostly, a certain degree of error is acceptable but only for some applications, however, others can’t tolerate even a small bit.

That’s why a mandrel bender must be used to prevent bending issues and errors. It allows you to maintain a highly precise and exceptionally functional performance of tube bending machines. 

why is mandrel important


What is the Proper Way of Using a Mandrel?

Usually, a mandrel is considered more as a pipe bending die than a tool. You can easily install and use a mandrel without any worries, as it is quite straightforward to use. 

The mandrel is held and secured in a position and the tube to be bent is slowly pulled over it. As the pressure is applied the mandrel supports the inner radius of the tube and allows it to be stretched so that it can be bent perfectly without any damages.

The mandrel can be used for various types of pipes and tubes, except for the ones with an incredibly smaller inner radius. As they contain no additional space for the mandrel to be placed in. 

The mandrel needs to be placed in the perfect position. The pipe can still encounter wrinkling or any other issue if the mandrel is fixed quite deep or more of its portion is outside the pipe. 


Materials Used for Mandrel Production

Apart from mandrel position inside the tube, its composition also determines the extent to which it can prevent tube wrinkling. Using a mandrel with proper material is quite necessary to prevent pipe damages and maintain the durable performance of the mandrel.

Most mandrels are made using an aluminum-bronze alloy or tool steel with rigid chrome plating. The composition of a mandrel should be selected in contrast to the pipe material you intend to bend. 

Aluminum-bronze alloy combination is used while bending pipes and tubes made of rather hard materials. It can be used to attain precise results by bending stainless steel, titanium, and Inconel-based pipes.

Alternatively, chromed-plated steel mandrels can’t be used for stainless steel pipes and tubes. They are mostly compatible with mild hard materials including, steel, copper, aluminum, and some soft materials.

Sometimes, a chromed mandrel can offer better performance as compared to aluminum alloy while bending titanium and Inconel pipes.

Many other materials and coatings can be used for the process.


Types of Mandrels

There are many different types of mandrels available on market. The style and material of a mandrel depend upon your bending requirements i.e. outside diameter (OD), and wall thickness (WT) of the tube to be bent.

You can find various mandrels ranging from simpler design options to incredibly complex ones. Here are some prominent types of mandrels designed exclusively for distinctive operation necessities:

  • Ball Mandrel

A standard ball mandrel is one of the most eminent types of the mandrel used to support a tube. It is designed to offer exceptional internal support to a tube beyond curvature depending upon the number of segments placed inside the entire bend.

The mandrel can be used with pipes having regular wall thickness (wall factor from 15 to 70), and an average radius.

You can calculate the wall factor of a tube by using this formula:

Wall factor = Outside diameter/Wall thickness

Normally, the ball mandrels can stretch in all planes. As the name suggests, the mandrel can move in multiple directions, this flexibility allows the formation of multi-radius dies. You can also use a single-plane mandrel if required but they can’t offer exceptionally precise operations. 

The mandrel is fixed and used in alliance with a wiper die clamp and pressure die while bending pipes with normal wall thickness. 

ball mandrel
  • Plug Mandrel

A plug mandrel is a solid rod used exceptionally for heavy thick-walled tubes and a larger radius. It is mostly used for international pipe sizes (IPS) operations with no help from wiper dies. 

  • Formed-tip Mandrel

A formed-tip mandrel is a variant of a plug mandrel, but it contains a radius cut at its tip to match the bending radius for creating more precise and damage-free bends. A formed end offers exceptional support to the tube interior. 

Such mandrel is normally used for heavier thick-walled tubes with an average radius. The mandrel is incredibly effective against heat exchange tube bending. 

  • Inserted-ball Mandrel

Inserted-ball mandrel contains a replaceable nosepiece making it appropriate for various high-volume bending operations. When the nosepiece is damaged or worn down, it is more cost-effective to only replace it instead of replacing the whole mandrel shank.

  • Thin Wall Mandrel

The thin wall mandrel also known as the close-pitch mandrel is widely used for thinner walls with a wall factor of 70 or more and a tight radius. Ultrathin-walls or ultra-close pitch mandrel is a modification of thin wall mandrel and can be used for the thinnest walls wall factor of 200 or more) with the tightest radii.

A thin or ultrathin mandrel shouldn’t be preferred over a standard mandrel. Apart from their numerous benefits, they have a rather fragile design.



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