How to call out a hem fold on sheet metal drawings?

Introduction

Welcome to our comprehensive guide on how to call out a hem fold on sheet metal drawings. As engineers with a manufacturing background, accurately specifying features such as hem folds is crucial to ensuring the quality and integrity of the final product. 

Understanding Hem Folds

Before we discuss how to call out a hem fold on sheet metal drawings, let’s first understand what a hem fold actually is. A hem fold is a type of fold where the edge of a sheet metal component is folded back on itself to create a smooth, rounded edge.

This not only improves the appearance of the part but also provides added strength and rigidity.

Why Use Hem Folds?

There are several reasons why hem folds are commonly used in sheet metal fabrication. One of the primary reasons is to eliminate sharp edges, which can be a safety hazard in certain applications.

Hem folds also enhance the overall aesthetic of the part, creating a more finished and professional look.

Additionally, hem folds increase the structural integrity of the component by reinforcing the edges and preventing distortion or warping over time. This is particularly important in applications where the part is subjected to mechanical stress or load-bearing requirements.

How to Call Out a Hem Fold

Now, let’s dive into the specifics of how to properly call out a hem fold on your sheet metal drawings.

When specifying a hem fold, it is crucial to provide clear and detailed instructions to ensure that the fabrication process is carried out accurately. Here are some key steps to follow:

• Dimensional Requirements

Specify the exact dimensions of the hem fold, including the width of the fold and the overall thickness of the material after folding. This information is critical for the fabricator to accurately reproduce the hem fold according to your design specifications.

• Bend Radius

Clearly define the bend radius of the hem fold, which will determine the curvature of the folded edge. The bend radius should be appropriate for the material thickness and type of sheet metal being used to ensure proper forming without cracking or deformation.

• Material Type and Thickness

Provide information on the type of material being used and its thickness, as this will impact the feasibility and precision of the hem fold. Different materials require different techniques and tools for forming hem folds, so be sure to specify the material properties accurately.

• Hem Fold Symbol

Use the appropriate hem fold symbol on your sheet metal drawing to indicate where the fold should be made.

The symbol typically consists of a straight line representing the edge to be folded and a curved arrow indicating the direction of the fold. This visual representation helps clarify the location and orientation of the hem fold.

• Callout Notes

Include detailed callout notes next to the hem fold symbol to provide additional instructions or specifications.

These notes can address specific forming techniques, tolerance requirements, or any other relevant details that the fabricator needs to know to accurately produce the hem fold.

Conclusion

In conclusion, calling out a hem fold on sheet metal drawings requires attention to detail and precise communication of design intent.

By following the guidelines outlined in this article, you can ensure that your hem folds are accurately fabricated and meet the necessary quality standards.

Remember to provide clear dimensional requirements, bend radius specifications, material details, and use the appropriate symbols and callout notes to convey your design instructions effectively.

Mastering the art of calling out hem folds will not only enhance the functionality and durability of your sheet metal components but also streamline the manufacturing process for optimal results. Thank you for reading, and happy designing!