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How to Design Your Sheet Metal Parts to Accommodate Hardware

Published on September 25, 2024

Designing sheet metal parts to accommodate hardware is a critical aspect of precision sheet metal fabrication. Whether you are working on consumer products, automotive components, or architectural applications, understanding the intricacies of metal fabrication processes can significantly influence the final product, reduce costs, and improve overall efficiency. In this guide, we share essential tips for designing sheet metal parts that seamlessly integrate with various types of hardware.

Sheet Metal Design: From Material to Product

Sheet metal design involves transforming a flat sheet of metal into a complex shape through cutting, bending, and forming. The goal is to produce a finished product that meets specific requirements while ensuring manufacturability and cost-effectiveness. The design phase is crucial as it sets the foundation for the manufacturing process.

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How to Select the Right Materials

Choosing the right material is one of the most important decisions in sheet metal design. The type of material used affects the strength, weight, corrosion resistance, and overall performance of the final product. It also influences the types of hardware that you will use as part of your product. Common sheet materials include:

Stainless Steel: Known for its corrosion resistance and durability, stainless steel is ideal for applications requiring high strength and a clean finish. It is commonly used in automotive components, consumer products, and architectural applications.
Galvanized Steel: This steel type is coated with zinc to enhance its corrosion resistance, making it suitable for outdoor and high-moisture environments.
Aluminum: Lightweight and corrosion-resistant, aluminum is a preferred choice for products where weight is a concern, such as in aerospace and automotive industries.
Cold Rolled Steel (CRS): This material offers good surface finish and is commonly used in automotive and appliance industries.

Hardware Types and Their Applications

Selecting the right hardware is critical for ensuring the functionality and longevity of the sheet metal assembly.

Rivets

Rivets are permanent mechanical fasteners used to join sheet metal components. They consist of a cylindrical shaft with a head, and are inserted into pre-drilled holes. When installed, the rivet deforms, creating a secure bond. Rivets are ideal for a wide range of applications, accommodating various material thicknesses and shapes.

Blind Rivets: These are used when only one side of the assembly is accessible. Blind rivets are common in automotive components and are ideal for high-volume production.
Conventional Rivets: These require access to both sides of the assembly and are typically used for more permanent fixtures.
Tubular Rivets: Tubular rivets are fasteners with a hollow shaft, commonly used for joining materials where lightweight, strong, and permanent connections are needed, especially in high-volume production.
Solid Rivets: Solid rivets are durable fasteners with a solid shaft, used for creating permanent, high-strength joints in metal structures, commonly in aerospace, automotive, and industrial applications.

Screws

Screws are one of the most versatile and widely used types of hardware in sheet metal fabrication. They are essential for creating secure, reliable connections that can be easily assembled and disassembled, making them ideal for both permanent and temporary assemblies.

Types of screws for sheet metal:

Threaded Fasteners: These are commonly used for assembly purposes where disassembly might be required. They offer strong and secure connections, making them ideal for high-stress applications.
Self-Tapping Screws: These screws are designed to cut their own threads into the sheet metal as they are driven in, eliminating the need for pre-drilled holes. They are especially useful in applications where speed and efficiency are crucial.
Machine Screws: Machine screws require pre-drilled and threaded holes or the use of a nut. They offer precise control over the assembly, making them ideal for applications requiring tight tolerances.
Self-Drilling Screws: Also known as Tek screws, these combine the functions of drilling and fastening into one step, which saves time in assembly processes by eliminating the need for pre-drilling.

Bolts and Nuts

Bolts and nuts are essential hardware components in sheet metal design, providing strong, secure, and often removable connections. They are widely used in applications where high-strength fastening is required, and where components may need to be disassembled for maintenance or repair.

Types of bolts and nuts used in sheet metal:

Hex Bolts and Hex Nuts: These are the most common types, featuring a hexagonal head for easy tightening with a wrench. They are widely used in structural and industrial applications due to their strength and reliability.
Carriage Bolts: These have a rounded head with a square neck that prevents the bolt from spinning as the nut is tightened. Carriage bolts are often used in applications where a smooth, rounded finish on one side of the assembly is desired.
Lock Nuts: Lock nuts are designed to resist loosening under vibration. They can feature a nylon insert (nyloc) or other locking mechanisms that grip the threads of the bolt, providing additional security in dynamic environments.
Flange Bolts and Nuts: These come with an integrated washer-like flange that distributes the load over a larger area, reducing the risk of damage to the sheet metal and providing better hold.

How to Design Sheet Metal Parts | 9 Key Considerations to Optimize Your Designs

Key Considerations for Hardware Accommodation

When designing sheet metal parts, it’s essential to consider how the hardware will be integrated. This includes understanding the hardware’s purpose, selecting compatible materials, and ensuring the proper placement of holes and fasteners.

Material Thickness and Hardware Insertion

The thickness of the material plays a significant role in hardware insertion. Thicker materials can accommodate more robust fasteners, while thinner materials may require specific hardware to prevent deformation.

Minimum Material Thickness: The material thickness should be sufficient to hold the hardware securely. For example, when using threaded fasteners, the material should be thick enough to provide adequate thread engagement.
Minimum Hole Size: The size of the hole should match the hardware specification to avoid issues during the insertion process. Minimum hole size guidelines ensure that the hardware fits snugly without compromising the sheet metal’s integrity.

Hole Placement and Distances

Proper hole placement is critical for maintaining the structural integrity of the sheet metal and ensuring the hardware functions as intended.

Edge to Hardware Distance: The distance from the edge of the sheet metal to the hardware is crucial. Too close to the edge, and the material may tear during hardware insertion; too far, and the hardware may not function effectively.
Hardware to Hardware Distance: When multiple hardware pieces are required, maintaining a minimum distance between them is essential to avoid interference during assembly.
Bend Allowance: When placing holes near bends, it’s essential to consider bend allowance to prevent distortion during the bending process.

Bending Considerations

Bending is a fundamental aspect of sheet metal fabrication. However, improper bending can lead to issues like material cracking, inaccurate angles, or misaligned holes. Here are some key bending considerations:

Bend Radius and Bend Tolerances

Bend Radius: The bend radius is the inside curve of a bend. Choosing the correct bend radius is essential to avoid material cracking, especially in brittle metals like aluminum. A common rule of thumb is to keep the bend radius at least equal to the material thickness.
Bend Tolerances: Bend tolerances are the acceptable variations in the bend angle. Tight tolerances ensure precision but can be more challenging and expensive to achieve.

Compatibility and Galvanic Corrosion

Ensuring material compatibility is crucial in sheet metal design to prevent galvanic corrosion, which occurs when dissimilar metals contact each other in the presence of moisture. Proper design and material choices can significantly enhance the durability of your product.

Material Selection: Use metals with similar electrochemical properties, like stainless steel hardware with stainless steel sheet metal, to prevent accelerated corrosion. Avoid pairing dissimilar metals, such as aluminum with stainless steel, which can lead to rapid degradation.
Preventative Design: Implement isolation techniques like powder coatings or non-conductive washers to separate metals, and avoid sharp edges during manufacturing to reduce corrosion risks.

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7 Frequently Asked Questions About Designing Sheet Metal Parts to Accommodate Hardware

Designing sheet metal parts to accommodate hardware involves various considerations to ensure optimal performance and durability. Below, we answer common questions regarding material compatibility, joint types, vibration resistance, and more, providing insights to help you select the best hardware for your specific sheet metal applications.

1. What type of joint will you be using?

Permanent Joints: If the joint is intended to be permanent, rivets are a suitable choice as they create a strong, unmovable connection.
Removable Joints: For joints that need to be disassembled for maintenance or repairs, screws or bolts are preferable as they allow for easy removal and reassembly.

2. Will the assembly be subjected to vibration?

Vibration Resistance: Conventional or blind rivets are better for assemblies exposed to vibration as they maintain a secure connection.
Screw Loosening: Threaded fasteners, such as screws and bolts, may loosen over time with vibration, so they are less suitable for high-vibration environments.

3. What are the strength requirements for the joint?

High Strength: Nuts and bolts offer the highest tensile and shear strength, making them ideal for heavy-duty applications.
Moderate Strength: Conventional rivets provide good strength, while tapping screws and blind rivets are suitable for lighter loads or thinner materials.

4. Can all components be brought to an assembly machine?

Accessible Assembly: If parts can be moved to an assembly machine, various fasteners including nuts, bolts, and conventional rivets can be used.
Inaccessible Assembly: For parts that cannot be moved, blind rivets are ideal as they allow the riveting tool to be brought to the assembly.

5. Is access to the back of the joint possible?

Accessible Back: If you can access the back of the joint, conventional rivets and nuts and bolts are appropriate.
Inaccessible Back: Blind rivets and tapping screws are best for situations where the back of the joint is not accessible.

6. How much backup space is available for the hardware?

Sufficient Backup Space: Tapping screws require 9.5 to 15.9 mm (0.375 to 0.625 inches) of backup space to ensure proper fastening.
Limited Backup Space: When there is limited space, blind rivets are a better option as they require less backup space.

7. How hard is the sheet metal material?

Material Hardness: Hardware should be at least as hard as the sheet metal material. Self-clinching hardware should have a Rockwell B scale hardness at least 20 points higher than the sheet metal to ensure proper engagement and durability.

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