AVT 206 A&P - P2 - Developing Sheet Metal Flats - The Math Behind the Bends

Introduction

This tutorial will guide you through the mathematical principles behind bending sheet metal, particularly useful for those preparing for the FAA Airframe test. Understanding concepts like setback, bend allowance, bend radius, and sight lines is crucial for accurately creating sheet metal flats. This guide will simplify these concepts and provide practical formulas to apply when bending metal.

Step 1: Understand Key Concepts

Before diving into the math, familiarize yourself with the following terms:

• Setback: The distance from the bend line to the back of the bend. It helps determine the overall length of the flat sheet.
• Bend Allowance: The additional length of material needed to accommodate the bend. It is essential for ensuring the final product meets size specifications.
• Bend Radius: The radius of the curve at the bend. A larger radius requires more material than a smaller radius.
• Sight Lines: Reference lines used to visualize the bend on the sheet metal.

Step 2: Calculate Setback

To calculate the setback, follow these guidelines:

1. Measure the bend radius (R).
2. Use the formula for setback:
   • Setback = R (Bend Radius) + Material Thickness
3. Ensure your measurements are consistent in units (inches or millimeters).

Step 3: Calculate Bend Allowance

Calculating the bend allowance is critical for accurate metal bending. Use the following steps:

1. Determine the bend angle (A) in degrees.
2. Measure the material thickness (T).
3. Apply the formula:
   • Bend Allowance = (A/360) × (π × (R + (T/2)))
4. This formula accounts for the radius and thickness to ensure the flat piece fits after bending.

Step 4: Determine the Total Flat Length

To find the total flat length required for your sheet metal piece, combine the calculated values:

1. Use the formula:
   • Total Length = (Length of the flat piece) + (Bend Allowance × Number of Bends) + (Setback × Number of Bends)
2. Make sure to adjust for any additional features or cuts in your design.

Step 5: Apply to Non-90 Degree Bends

For bends that are not 90 degrees, the process is similar but requires an adjustment in the bend angle:

1. Follow the same calculation methods for setback and bend allowance.
2. Ensure you input the correct bend angle into the formulas to get accurate measurements.

Conclusion

Understanding the math behind bending sheet metal is essential for achieving precise results in your projects. By mastering concepts like setback, bend allowance, and bend radius, you can create accurate sheet metal flats. Practice applying these formulas to different bending scenarios, and consider watching further tutorials to expand your skills, especially for non-90 degree bends.