Rivets for Sheet Metal Fabrication(sheet metal rivets Derrick)
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What is a Rivet?
A rivet is a mechanical fastener that is used to join two or more pieces of material. Rivets come in a wide variety of head shapes, sizes and materials but they generally consist of a smooth cylindrical shaft and a head on one end. The end opposite the head is called the tail. The shaft of the rivet is inserted through pre-drilled holes in the materials being joined. The tail is then deformed so that it expands, pressing tightly against the underside of the material and forming a second head. The rivet holds the materials together through clamp force created by the deformed tails pressing outward on the underside of the joint.
Benefits of Rivets for Sheet Metal
There are several reasons why rivets are commonly used for joining sheet metal:
- Permanent and Secure Fastening - Once installed, rivets form a permanent connection that will not come loose over time and vibration like screws or bolts can. The flaring of the rivet tails creates a tight clamping force that firmly joins the materials.
- No Threads Needed - Installing rivets does not require pre-forming threads in the sheet metal pieces being joined. This avoids the need for threading tools and tapped holes.
- Allows Movement - Unlike welding, riveting forms a joint that still allows some relative movement between the joined pieces. This can be advantageous when joining dissimilar metals or for assemblies that require a degree of flexing.
- Smooth exterior finish - Properly set rivets form smooth flanged heads on the exterior surface that has a clean, finished look.
- Quick Installation - Rivets can be installed very quickly with either manual or pneumatic rivet tools, allowing for efficient fabrication and assembly.
- Variety of Materials and Sizes - Rivets come in a range of materials, head styles and shaft diameters to suit different design needs and material thickness. Common materials include aluminum, steel, copper, stainless steel, and Monel.
Using Rivets with Sheet Metal
Installing rivets to join sheet metal components successfully requires following some guidelines on hole sizing and placement:
- Hole Diameter - For the rivet shaft to fit through the holes in the sheet metal pieces, the holes must match the diameter of the shaft. Allowing some clearance around the shaft, such as .005” greater diameter, facilitates insertion.
- Hole Alignment - Any misalignment between holes can prevent proper rivet setting. The holes should be carefully pre-drilled to align perfectly between the two or more pieces of sheet metal stacked together.
- Hole Spacing - There should be adequate material between holes to prevent distortion or cracking during rivet setting. Generally at least 3 times the hole diameter is recommended between rivet centers.
- Hole Placement - Holes should be positioned and spaced such that the joined materials share the load equally. Setting rivets near the edges and ends of pieces helps prevent distortion.
- Clamping - Pressure must be applied to clamp the materials tightly together during rivet setting to allow proper flaring of the rivet tails. Clamping can be done by hand, jigs, vacuum or magnets.
- Access - There must be sufficient access to the side of the materials where the rivet heads are formed for tools to be positioned during installation.
Rivet Setting Methods
There are two main techniques used to mechanically set and flare the tails of rivets for sheet metal fabrication:
Impact Riveting - This involves using a hammer or rivet gun to strike and flare the tail. The force of the impact spreads the tail and compresses the rivet shaft to clamp the materials. Rivet guns are pneumatic tools that repeatedly strike rivet heads at a controlled force.
Squeeze Riveting - Squeeze riveting uses hydraulic jaws that encompass the rivet and materials being joined. As hydraulic pressure squeezes the jaws closed, an axial force is applied to the rivet. This flare the tails and compresses the shaft in a controlled manner. Squeeze riveting allows more uniform and repeatable setting compared to impact riveting.
Rivets provide an effective and efficient means for securely and permanently joining sheet metal while allowing flexibility in the design and fabrication process. By following proven guidelines on hole sizing and placement, rivets can be successfully installed using impact or squeeze setting methods to withstand vibration and structural loading over the lifetime of the product. With the range of head styles and materials available, rivets are a versatile fastening solution for virtually any sheet metal application. CNC Milling CNC Machining