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  • Writer's pictureBoro Park Manufacturing and Sheet Metal Fabrication

Understanding the K-Factor in Sheet Metal Fabrication

K Factor in Sheet Metal Fabrication
K-Factor in Sheet Metal Fabrication

Leveraging the K-Factor in Sheet Metal Fabrication for Enhanced Manufacturing Outcomes

Precision is paramount in sheet metal fabrication.

Accurately bending sheet metal into desired shapes directly influences the functionality and assembly of the final products.

A critical concept here is the "K-Factor," vital in bending and bridging design with manufacturing, especially when using tools like SolidWorks.

This post explains the importance of the K-Factor, its calculation, and its application in different scenarios, specifically focusing on its integration from SolidWorks designs to production.

What is the K-Factor?

The K-Factor is a crucial parameter in sheet metal fabrication that helps predict how much the metal will stretch or compress during bending.

It represents the location of the neutral axis—where the material neither stretches nor compresses—relative to the inside bend radius, expressed as a fraction of the material thickness.

Why Use the K-Factor?

Incorporating the K-Factor in manufacturing processes offers several benefits:

  • Enhanced Accuracy - This allows for precise calculation of the Bend Allowance, ensuring that the product's final dimensions are accurate and meet design specifications.

  • Material Efficiency - Accurate Bend Allowance calculations minimize trial and error, significantly reducing material waste.

  • Improved Design Feasibility - Designers can use the K-Factor to verify that the physical production of their designs is feasible, adjusting their models in the design phase before any metal is cut.

  • Consistency in Production - Manufacturers can achieve consistent quality across multiple batches and production runs by standardizing bending operations.

The K-Factor Equation

The K-Factor is utilized to calculate the Bend Allowance (BA), which is crucial for determining the correct length of the flat sheet metal needed to achieve a desired bend:

k factor in sheet metal fabrication


  • 𝑅 is the inside bend radius

  • θ is the bend angle in degrees

  • 𝑇 is the material thickness

  • 𝐾 is the K-Factor

Application Across Material Types

Different materials respond differently under stress due to their varying properties, like elasticity and composition.

For instance:

  • Aluminum tends to have a higher K-Factor because it is more pliable and stretches.

  • Steel exhibits a lower K-Factor as it is stiffer.

  • Stainless Steel requires a K-factor between aluminum and steel, reflecting its unique blend of stiffness and ductility.

Integrating K-Factor From SolidWorks Design to Production

SolidWorks software is extensively used in sheet metal design due to its powerful tools that simulate real-world variables, such as material thickness and bend radius.

Here's how incorporating the K-Factor benefits the transition from SolidWorks designs to physical production:

  1. Design Accuracy: SolidWorks allows the K-Factor to be entered into the software, which calculates flat patterns and bend allowances automatically. This ensures that the designs are production-ready.

  2. Prototype Reduction: By accurately simulating the bending process in SolidWorks, the need for physical prototypes can be reduced, saving time and resources.

  3. Seamless Communication: When designers use accurate K-Factors in their SolidWorks models, the data can directly inform CNC machines in production, ensuring that the physical parts closely match the digital designs.

Determining the K-Factor for Your Shop's Dies

Determining the K-factor for your shop's specific tooling and dies is crucial for optimizing sheet metal fabrication processes. Here's a step-by-step guide on figuring out the K-factor for your shop's dies. This method is practical, requiring some trial and error, but it ensures precision in your bends.

Step 1: Material Selection

Start by selecting the type of material and the specific thickness you intend to work with. This is crucial as the K-Factor can vary significantly between different materials and thicknesses. For example, aluminum will generally have a different K-Factor than stainless steel.

Step 2: Prepare Sample Pieces

Cut several small sample pieces of the material. Each piece should be large enough to handle and measure but small enough to save materials. A typical size might be a strip 100mm wide and 200mm long. This size allows enough room for bending and measuring the flanges without using excessive material.

Step 3: Marking and Bending

Mark a line in the center of each sample piece to indicate where the bend will occur. Using your shop's standard bending equipment and dies, bend each sample at a common angle used in your productions, such as 90 degrees. It's helpful to perform this step on multiple pieces to verify consistency.

Step 4: Measure the Results

After bending, use precise measuring tools such as a caliper or micrometer to measure the resulting flange lengths from the apex of the bend to the end of the flange. Record these measurements carefully.

Step 5: Calculate the Neutral Axis

The K-Factor is essentially the ratio of the distance from the inside face to the neutral axis divided by the material thickness.

To find this:

  • Assume a provisional K-Factor (common starting points are 0.33 for steel and 0.42 for aluminum).

  • Use the formula to calculate the BendAllowance:

k factor in sheet metal fabrication


  • 𝑅 is the inside bend radius (can be measured from your bent sample)

  • θ is the bend angle (90 degrees in this case)

  • 𝑇 is the material thickness

  • 𝐾 is the assumed K-Factor

Step 6: Compare and Adjust

Compare the calculated Bend Allowance to your bent sample's measured length. If there's a discrepancy, adjust the K-Factor upward if the actual length exceeds the calculated length and downward if less. This adjustment is based on the position of the neutral axis moving closer to the inside face of the bend as the material stretches.

Step 7: Iterate

Repeat steps 3 to 6 using the new K-Factor until your calculated Bend Allowance matches the measured value closely. This iterative process fine-tunes the K-Factor to your specific equipment and materials.

Step 8: Standardize and Document

Once a consistent K-Factor is determined, document this value along with the associated material type, thickness, and bend radius. Create a reference table for these values for future projects. This standardization helps maintain consistency in production and reduces setup times.

Determining the K-factor for your shop's dies might seem tedious initially, but it's an investment in accuracy and efficiency.

By systematically testing and adjusting the K-factor, you can ensure that your bends are precise, reducing waste and increasing the predictability of your sheet metal parts. This improves the quality of the final products and enhances the operational efficiency of your fabrication processes.


Understanding and accurately implementing the K-Factor in sheet metal fabrication significantly enhances the link between digital design in SolidWorks and physical manufacturing.

It optimizes material usage, ensures product accuracy, and streamlines manufacturing.

For manufacturers in the metal fabrication industry, mastering the K-Factor is not just a technical necessity; it's a competitive advantage that ensures consistency, efficiency, and quality in production.

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