Why is wall factor important?

Learn how this can impact a tube bending project

Wall factor, the ratio between tube outside diameter and wall thickness, is one of the key elements used to assess the difficulty of a tube bend. A wall that is thin compared to the tube outside diameter requires more support at the arc of the bend to prevent wrinkling or collapse. In this case, use of a mandrel along with other tooling is necessary to achieve good quality. 

The other important element is the “D” of bend, the diameter of the tube in relation to the bend radii, often called out by however many times larger it is than the value of D. For example, a 2D bend radius of a 3” OD tube would be 6”. The higher the number for the D of the bend, the easier it is to form the bend. And, the lower wall factor, the easier the bend. This correlation, between wall factor and D of bend, helps determine what will be needed, such as the type of tooling, to begin a tube bending project.  

Some project specs call out thinner walled tube or pipe to manage material costs. However, a thinner wall may require more production time to maintain the shape and consistency of the tube through the bend and eliminate the chance of wrinkling. In some cases, these added labor costs may outweigh the material savings.

If there’s flexibility in your part design, this can help as you weigh all of the factors involved to determine the best approach for your project. Please feel free to contact us with questions on manufacturing timelines and costs. 

This blog was authored by Marshall Arndt, Estimating Engineer, Sharpe Products. Marshall can be reached at marshalla@sharpeproducts.com.