4 Methods for Creating Sheet Metal Threaded Holes

Sheet metal processing is a crucial method in metalworking, involving the cutting, bending, folding, and welding of metal sheets into products of various shapes and sizes. It's widely applied in fields such as machinery, electronics, construction, and home appliances. Due to the limitations of sheet metal thickness, it can be challenging to create threaded holes in sheet metal using conventional methods for assembly purposes. This article will introduce several methods for creating threaded holes in sheet metal.

Tapping

Tapping is the most common method of threading holes. However, due to the thin nature of sheet metal, when tapping, it's important to consider factors such as the number of thread turns. The following principles are usually observed:

• For thin sheets (t<3mm), fine threads are preferable;
• The number of threads should be at least 1.5 turns, with 2 or more turns recommended;
• Very thin sheet metal (t<1mm) is not suitable for tapping; self-tapping screws are recommended.

Here is a simple algorithm for matching metric thread specifications to the minimum thickness of sheet metal:

For example, 1.5mm sheet metal can be tapped for M3 holes, and 3mm sheet metal can be tapped for M6 holes, and so on. Directly tapping threads into sheet metal can result in fewer threads and lower strength, hence it is recommended for use with materials like SPCC, SECC, SS41, SUS304, and it's advised not to bear excessive loads.

Press-in Nuts

Press-in nuts, also known as embedded nuts, press rivet nuts, or cap nuts, are fasteners used in sheet metal processing. They can be pressed into the sheet metal using a cap machine, forming a threaded hole. During design, it's only necessary to consult the supplier's cap specifications and corresponding hole diameters, and mark them on the drawing.

Sheet metal press-in nuts have the following features:

• Easy installation:
  They can be quickly installed using a nut pressing machine, requiring only a hole to be made during the cutting process, without the need for additional drilling or tapping.
• Wide range of applications:
  Suitable for various types of sheet metal, including steel, aluminum, and stainless steel.
• Low cost:
  Relatively inexpensive, making them suitable for mass production.
• By choosing special types of press rivet studs, blind holes can be created in sheet metal. 盲孔.

Rivet Nuts

Rivet nuts are fasteners designed for thin sheet metal or thin-walled materials, allowing for the quick and effective creation of threaded connection points without needing access from the other side. Rivet nuts are made of metal with a threaded segment and a specially designed head that can be fixed to the material by pulling. During installation, the rivet nut is inserted into a pre-drilled hole, and then a special tool is used to pull the tail of the rivet nut, causing its back to expand and form a fixed head on the other side of the material, thereby securing the rivet nut.

Advantages

1. Quick installation: Fast installation speed, suitable for large-scale or batch production, significantly improving assembly efficiency.
2. No need for backside access: Installation does not require access from the other side of the material, making it very suitable for space-limited or single-sided access applications.
3. Strong fixing force: The expanding head formed by the rivet nut in the material provides a strong fixing force, increasing the strength and stability of the connection.
4. Suitable for various materials: Rivet nuts can be used in a variety of thin-walled materials, including metals and plastics, increasing their application flexibility.

Disadvantages

1. Special tool requirement: Installation requires a special rivet gun or rivet nut tool, which may increase tool costs.
2. Single-use: Once installed, the rivet nut cannot be removed and reused, potentially increasing the difficulty and cost of maintenance or replacement.
3. Material thickness limitations: There are certain thickness range limitations for the materials suitable for rivet nuts, making them not the best choice for overly thick or thin materials.
4. Installation quality depends on skill: The quality of rivet nut installation largely depends on the operator's skill and experience, improper operation may result in insufficient connection strength.

Weld Nuts

Weld nuts are a common method of fixing used on thin sheet metal components, especially where reliable threaded connection points are required. This method fixes nuts to the metal surface via welding technology, providing a joint for bolts or screws. Weld nuts are suitable for various metal materials, including stainless steel, carbon steel, and aluminum alloys. Weld nuts often have special designs, such as protrusions, which help in the fusion process during welding, ensuring a solid metal connection between the nut and the base material. During welding, the weld nut is precisely positioned on the predetermined location on the sheet metal, then fused to it using resistance welding (spot welding) or another suitable welding method.

Advantages

1. Durable and vibration-resistant: Weld nuts provide a very strong fixing method, durable and resistant to vibration, suitable for high-load or vibration environments.
2. Good electrical connection: For applications requiring good electrical grounding or conductivity, weld nuts can provide solid metal-to-metal contact.
3. Space-saving: Weld nuts do not require operation from the other side of the sheet metal, saving space and suitable for space-limited designs.
4. Suitable for various materials: Can be used with a variety of metal materials, offering high application flexibility.

Disadvantages

1. Professional equipment and skills required: Weld nuts require professional welding equipment and skilled operation, potentially increasing manufacturing costs.
2. Heat-affected zone issues: The high temperatures generated during welding can create a heat-affected zone around the metal, affecting material properties, especially on thin sheet metal.
3. Limited post-welding adjustment: Once welded, adjusting or correcting the position becomes more difficult, posing a challenge to manufacturing tolerance.
4. Potential impact on appearance: The welding process may leave marks or welding scars on the sheet metal surface, requiring further surface treatment for applications requiring a perfect appearance.

Conclusion

Each method has its applicable scope, advantages, and disadvantages. The choice of which method to use depends on specific application requirements, the type of materials used, and considerations for production efficiency.