Riveting in Sheet Metal Fabrication(bead blast material Dempsey)
- source:GAENOR CNC Machining
What is a Rivet?
A rivet is a mechanical fastener that consists of two main parts - the rivet body and mandrel. The body is a tube or shaft of metal with a head on one end. The mandrel stems from the opposite end of the body and is used to flare out the rivet when installed.
When joining sheet metal, holes are drilled through the sheets to be joined. The rivet body is inserted into the aligned holes. Using a riveting hammer, dolly, or specially designed rivet gun, the mandrel is pulled or driven through the body. This flares out the body on the back side of the joint, creating a wide footprint that holds the sheets together. The excess mandrel is then sheared or broken off.
Benefits of Riveting:
- Strong Joints - The wide footprint created by flaring the rivet body distributes load over a larger area, allowing rivets to withstand significant shear and tensile stresses. Properly installed rivets form very sturdy joints.
- Lightweight - Rivets add very little mass or thickness to a sheet metal assembly. This makes them ideal for applications where minimizing weight is important.
- Vibration Resistance - The flared body of the rivet effectively locks sheets together, resisting the effects of vibration or shock loading that could loosen other fasteners like screws or bolts.
- Quick Installation - Riveting is generally faster than welding or using adhesives when assembling sheet metal components. It also requires less preparation of the materials being joined.
- Economy - Rivets are inexpensive relative to other joining methods. Both installation tooling and the rivets themselves have low costs compared to welding equipment and wire/rod.
- No Heat Affected Zone - The riveting process does not create any heat like welding. This avoids potential distortion or metallurgical damage that can occur in heat affected zones around welds. Riveting is suitable for temperature sensitive materials.
- Appearance - Properly set rivets have a clean, finished look. In applications where appearance is important rivets can provide an aesthetically pleasing fastening method.
Types of Rivets for Sheet Metal:
Several varieties of rivets are commonly used to fabricate sheet metal products:
- Solid/Round Head Rivets - As the name suggests, these have a solid shank and rounded head. They are the most commonly used rivet type due to their simplicity and economy.
- Countersunk Head Rivets - These have a flat, countersunk head that sits flush with the surface of the sheet. Used when a low profile smooth surface is needed.
- Large Flange Rivets - These have oversized flange heads that cover the joint and surrounding area. They help ensure water tightness and are frequently used in ducting.
- Structural Rivets - Designed to withstand higher stresses. Typically have larger diameters than other types and flare to a larger footprint.
- Blind Rivets - Used for joining sheets where access is only available to one side. The body collapses on itself rather than flaring outward.
- Self Plugging Rivets - Combine the sealing properties of solid shank rivets with the convenience of blind rivets. The mandrel snaps off below the surface, plugging the hole.
- Drive Rivets - Also known as screw or threaded rivets. They have external threads that allow installation with a hex driver rather than hammering/pulling.
The basic process for riveting sheet metal components is:
1. Material Preparation - Sheets to be joined are cleaned and aligned. Holes are drilled or punched to accept the rivet bodies. Hole sizes match the rivet shank diameter.
2. Rivet Selection - Proper rivet length is determined based on material thickness. Rivet diameter is chosen based on joint strength needed.
3. Insertion - Rivet bodies are inserted into the aligned holes. Rivet heads should rest flush against the sheet surface.
4. Setting - Using the appropriate riveting hammer, dolly, or tool, the rivet mandrels are pulled/driven to flare the rivet bodies. This expands the rivet, clamping the sheets together.
5. Trimming - Any excess mandrel is trimmed off flush with the rivet head using nippers. The set rivet should have a full, spherical head.
6. Inspection - The installer should inspect each rivet visually and by feel to ensure proper setting. Loose rivets must be replaced.
Installing rivets correctly requires some skill and practice to get a feel for how much pulling/hammering is needed. Using quality equipment also improves results and productivity. But with appropriate training and tools, riveting sheet metal components is a straightforward and reliable fabrication method.
Applications for Riveting:
Rivets have long been used in numerous sheet metal fabrication applications:
- Aircraft Construction - Rivets are the preferred method of assembling airplane fuselages, wings, and other components. The aircraft industry makes extensive use of solid and blind rivets.
- HVAC Ductwork - Roundhead rivets are commonly used to fabricate rectangular duct sections. Large flange rivets help create leakproof spiral duct joints.
- Electronics Enclosures - Rivets neatly fasten sheet metal electronics housings without adding thickness. Countersunk rivets provide a flush surface.
- Automotive Parts - From body panels to exhaust components, rivets offer automakers a proven way to assemble sheet metal components.
- Metal Building Products - Roofing, siding, downspouts, and gutters are often assembled from sheet metal using rivets. They resist leakage and wind damage.
- Furniture and Displays - Rivets allow secure and attractive joining of sheet metal furniture frames, retail displays, and decorative panels.
- Storage Containers - Roundhead and blind rivets are an economical fastening method for assembling storage bins, cabinets, and boxes from sheet metal.
Rivets continue to be a go-to fastening method for working with sheet metal across many industries. Their flexibility, strength, and ease of use make rivets a primary choice for both manufacturing and custom fabrication. With a long history and proven performance, riveting will remain a mainstay of quality sheet metal construction. CNC Milling CNC Machining