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SOLIDWORKS for Fabrication: What is a K-Factor?

Monday August 28, 2023 at 8:00am

In the world of sheet metal fabrication, precision is paramount.

Every bend, every angle, and every material thickness factors into the creation of a successful sheet metal part. One key aspect that plays a crucial role in achieving accuracy is the bend allowance.

Let’s explore what bend allowances and K-Factors are, and show you how they apply in fabricating sheet metal with SOLIDWORKS.

Each bend and fold in a sheet metal part transforms a flat piece of metal into a functional and often intricate component.

However, this transformation is not without its challenges, one of which involves determining the correct length of material needed for bending. This is where the bend allowance comes into play.

The Three Bend Allowance Methods

SOLIDWORKS offers three distinct methods for calculating bend allowances: the K-Factor, bend calculation, and bend allowance/deduction. While each method serves the same fundamental purpose to determine the correct flat pattern length, they vary in complexity and precision.


The K-Factor is a dimensionless value between 0 and 1 that serves as a compass within the world of sheet metal bending. It describes the location of the neutral axis - a point where neither compression nor tension occurs - within a material's thickness.

The neutral axis is crucial because it affects how the material behaves during the bending process.

The K-Factor method is commonly used, and relies on predefined values based on material thickness and bend radius. It's a quick and relatively reliable way to calculate bend allowances.

The table below (with Alt text) highlights the recommended values to use for K-Factors.

A table containing recommended values for Sheet Metal K-Factors. When the radius is less than the material thickness, use a K-Factor of 0.25.  When the radius is equal to a value between the material thickness and double the material thickness, use a K-Factor of 0.33.  When the radius is greater than double the material thickness, use a K-Factor of 0.5.


This method takes a more analytical approach, utilizing an equation to calculate the K-Factor based on various parameters, including material thickness, bend radius, and bend angle.

It provides a higher degree of accuracy, especially for intricate designs, as it determines the exact position of the neutral axis.


The most accurate of the three, this method involves practical testing to determine the correct values for bend allowance or bend deduction.

Bend Allowance Equation

It's particularly useful when precision is paramount and when working with unique materials or bending equipment.

Bend Deduction Equation

Optimising Bend Accuracy with SOLIDWORKS

SOLIDWORKS 3D CAD is widely used by sheet metal fabricators to create, simulate, and analyse sheet metal parts. Within SOLIDWORKS, the bend allowance plays a pivotal role in ensuring that the virtual design aligns seamlessly with the physical outcome.

SOLIDWORKS calculates flat patterns from material thickness, bend radius, and bend angle values. The software then employs the K-Factor value to calculate the bend allowance required.

For greater precision, the bend calculation method can be employed, automating the process based on industry standards and specific parameters.

All of these bend allowances can be stored in bend or gauge tables, and called upon when required.

Just remember to update your tables as your brakes and tooling wear or are replaced!

Looking for More Tips?

Sign up to our CPD-accredited training courses.

It doesn’t matter whether you’re a complete beginner or are intimately familiar with CAD, our friendly and expert trainers are ready to help you get the most out of SOLIDWORKS, either online or in a classroom local to you.

We also have a load of free SOLIDWORKS tutorials across our site, or you can check out our YouTube channel for more tips and tricks.

Don’t forget, with a SOLIDWORKS subscription, you can contact our expert Technical Support team to help you out with new commands and modelling tips.

Call us on 01926 333 777 or drop an email to and one of our certified SOLIDWORKS Engineers will be in contact.

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