Effective joining of sheet metal parts is a critical stage of the sheet metal fabrication process. In this article we’ll take a look at five standard methods of joining sheet metal and discuss how you decide the best method to use to manufacture your sheet metal product.
What are the five standard methods of joining sheet metal?
Sheet metal fabrication of most products involves joining metal components together at some stage of the construction and assembly process. Once you go beyond simple shapes and surfaces, and start constructing boxes and more evolved structures it becomes necessary to fabricate them from multiple components that need to be joined together.
Let’s have a brief look at these techniques for joining sheet metals before considering how to choose which method or combination of methods is best for any sheet metal fabrication project.
Welding for strong sheet metal connections
Welding is the process of melting the metal to fuse components together, it is the strongest method of joining metals together, and is widely used across all metalworking industries. There are, however, several different welding techniques, which have different effects on the metals being joined. Because of the relatively clean finish, spot welding and arc welding using inert gas shielding are the preferred methods for sheet metal fabrication.
Low temperature soldering for delicate sheet metal structures
Soldering requires melting a lower temperature metal or alloy that flows into the gap between the sheets being joined, at temperatures up to 450C. For thin sheet materials it reduces the issue of distortion from welding, and can produce a very strong bond.
Soldering is a labor intensive method that requires skill to make clean joins with minimal finishing, but can be a valuable tool for the right project, especially with low melting point metals like the copper pipe in the image above. Brazing is a similar process for temperatures over 450C, and gives a stronger bond.
High strength riveting: a traditional sheet metal fabrication method
Historically, riveting may be associated with traditional ship building, and heavy construction, and it was a very commonly used technique before the development of reliable welding technology. Riveting is still a useful technique for sheet metal fabrication, although today it is more likely to be used to make ‘pop’ rivets in thin materials. Making a flat surface when riveting requires a counter-sink cut in the holes of the pieces being riveted, which adds complexity.
Adhesives offer simplicity but reduced durability when joining sheet metal together
Adhesives can be an excellent method of joining sheet metal together, but the working environment of the finished product needs to be taken into consideration when selecting adhesives, which have specific characteristics and failure modes depending on temperature, movement, and the presence of solvents. Most adhesives soften when heated, and this makes them unsuitable for many sheet metal fabrication applications.
Bolts & machine screws enable disassembly of sheet metal products
Bolts and machine screws are the only method of joining sheet metal in this list that can be reversed, enabling parts to be disassembled without difficulty. Assembly time may be increased by the use of bolts and screws, For screws it is usually necessary to add a process to cut threads into the sheet metal.
An alternative to cutting threads in the sheet material separately is to use machines that will drill and thread a hole at the same time, or press a threaded cylinder into the sheet metal, as shown in the image above from our factory in Taiwan. This offers a neat and effective solution that give a very reliable and workable result for rapid assembly.
How to decide which sheet metal joining method is best for your project?
When deciding which method to use to join sheet metal together, we need to take seven factors into consideration to decide the best method for any specific sheet metal fabrication project, so it’s not always a simple choice between a couple of options.
- Material thickness
- Joint strength
- Aesthetic appeal
- Production volume
- Heat distortion
- Surface preparation
- Assembly & disassembly
What are the strongest methods for joining sheet metal?
Welding and riveting are the strongest methods of joining sheet metals together, and riveting has the advantage of not requiring heat, but riveting needs to be countersunk, requiring more preparation, if a flat surface is required. Soldering and adhesives can provide a strong bond, but it can take more time to create a clean result when soldering.
When can you use adhesives for sheet metal fabrication?
Some modern adhesives are extremely strong and resistant to chemicals and solvents: epoxy glues are especially effective, but all adhesives come with the risk of mechanical failure as they do not match the material characteristics of the metal you are bonding together, requiring special techniques to make them conform to the metal surface. Adhesives are useful for applying decorative, contrasting, thin metal sheets to a project, for example, but welding is a better option to achieve a durable, stronger, result.
Bolts & machine screws enable easy assembly and disassembly
Bolts and machine screws with captive threaded sleeves are an excellent method that avoids the need for heat or adhesives and also maintains the option for disassembly of the finished product. For sheet metal boxes and enclosures that are lightweight, making them easy to assemble offers the flexibility to have them assembled by the end user, enabling savings on shipping volume.
Call us to discuss the best joining method for your sheet metal project
We can see that sheet metal fabrication uses different joining techniques to assemble components into the finished product. It requires a comprehensive understanding of these different joining techniques, their strengths and weaknesses, for a sheet metal fabricator to determine the most appropriate method to achieve strong, reliable, and visually pleasing results for their customers.
At Taiwa, our designers, engineers and technicians are expert in sheet metal joining as a key element of the fabrication process. This is why our customers can rely on us for high quality, reliable sheet metal fabrication of even the most complex designs. Contact us to discuss your sheet metal fabrication requirements and allow us to share our experience and skills to enhance your project.
