Riveting in Sheet Metal Fabrication(g&m codes Yvonne)

  • Time:
  • Click:12
  • source:BAGANZ CNC Machining
Rivets are a crucial fastening method in sheet metal fabrication. They create strong mechanical bonds between multiple sheets of metal or other materials. Compared to welding, riveting allows assembly and disassembly for maintenance or modifications. It is also cheaper than welding in many cases. For these reasons, rivets remain ubiquitous in aircraft, automobiles, appliances, electronics, and construction.
How Rivets Work
A rivet is a short cylindrical shaft with a head on one end. During installation, the rivet is placed in a pre-drilled hole through the materials being joined. The tail end is then upset and hammered, pressed, or bucked by a rivet gun. This causes the tail to mushroom and clamp the rivet in place. The deformed tail is called the shop head or buck-tail.
Rivets transfer load between joined members through shear stress across the rivet shank. Good rivets fill 60-80% of the hole after installation. This provides a tight fit that maximizes load transfer. The rivet head and shop head also clamp materials together longitudinally through compression.
Advantages of Rivets
Rivets have stood the test of time due to their combination of strength, reliability, and ease of use.
- Strong and reliable: When installed correctly, rivets form very strong joints. Rivet strength comes from compressive clamping force and shear strength of the deformed shaft. Multiple rows of rivets also distribute load across connections.
- Easy to install: Riveting is simple relative to welding or adhering. It only requires access to one side of a joint in most cases. Rivet guns allow quick installations with proper training.
- Reusable: Rivets can be drilled out and reinstalled if needed for repairs or modifications. This can save time and money compared to welds, which may require cutting and re-welding.
- Easy inspection: The characteristic mushroom shape of rivet heads and tails allow quick visual inspection to check for defects. Loose or sheared rivets are clearly evident.
- Material options: Rivets come in a wide range of metals, polymers, and composites. This allows matching rivet materials to the application for optimal strength and corrosion resistance.
Common Rivet Types
There are various types of rivets designed for different applications:
- Solid rivets: These are one-piece rivets made entirely from the rivet material. Common materials include steel, aluminum, copper, and Monel. Solid rivets suit many general sheet metal fabrication purposes.
- Blind rivets: Blind rivets can be installed where access is only available to one side of a joint. The mandrel stem is pulled through the rivet body to form the second head. Aircraft make widespread use of blind rivets for internal structures.
- Drive rivets: These rivets combine a solid rivet body with a tapered mandrel assembly. Rivet gun jaws press the mandrel to upset the rivet in place. Drive rivets allow very quick installation for high-volume production.
- Self-plugging rivets: These rivets have a hollow mandrel that locks into the rivet body. When set, the mandrel fills the rivet to create a leakproof connection. Self-plugging rivets are ideal for joining sheet metal that will contain liquids.
- Structural rivets: Structural rivets are designed for strength in critical mechanical joints. They are common in aircraft, trucks, cranes, and other applications. Materials like titanium increase shear and tensile strength.
Best Practices for Riveting
For optimal results, proper techniques and best practices should be followed when riveting sheet metal:
- Drill holes precisely: Holes must match rivet diameters very closely, typically within 0.002 inches. Loose rivets diminish strength, while tight holes impair setting.
- Deburr holes thoroughly: Any remnants of material around the hole edge should be removed. This ensures the rivet sits flush against hole walls.
- Select compatible materials: Using rivet and sheet materials with similar hardness and strength prevents cracking around holes.
- Position rivets correctly: Rivets should be centered in holes with the factory head against the preferred visible surface.
- Apply consistent pressure: Use rivet sets that match rivet head styles and diameters. Hold rivet gun perpendicular to material to avoid bending.
- Check set quality: Confirm rivets are set properly. Heads and tails should be concentric without cracks. Tug on rivets to check tightness.
- Follow recommended spacing: Rivets along edges and seams should be spaced based on standard guidelines for the materials and loads.
- Seal surfaces: Apply sealants or adhesives like acrylic latex caulk for waterproof riveted joints where needed. Allow proper cure time.
While welding may be required for very high strength demands, rivets cover a broad range of fabrication and repair applications. Their flexibility, economy, and proven performance ensure rivets will remain a go-to fastening method for working with sheet metal. Proper installation technique and following best practices allow fabricators to produce quality riveted products. CNC Milling