Riveting in Sheet Metal Fabrication(what are rivets used for Jay)

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Rivets have been used since ancient times to join pieces of metal together. In modern sheet metal fabrication, riveting is still a very common and useful technique. Rivets create strong permanent joints that can withstand vibration and stresses.
What is a Rivet?
A rivet is a mechanical fastener that connects two or more pieces of material. Rivets consist of two main parts - the rivet body and the rivet mandrel. The rivet body is a head on one end, a shank, and a second head formed on the other end during the riveting process. The rivet mandrel is inserted into the rivet body and fills the hole in the center of the rivet. As the tails of the rivet body are pressed together, the rivet mandrel spreads the rivet body, forming the second head.
The rivet body is commonly made of steel, aluminum, copper, or Monel. The material used depends on the materials being joined and the application. The mandrel is typically made of steel and allows the rivet body to deform as it’s compressed into the second head shape. After riveting, the mandrel is discarded.
Benefits of Riveting
There are several advantages to riveting in sheet metal fabrication:
- Strong joints - The deformation of the rivet body creates a strong joint that won’t come loose over time. Riveted joints withstand vibration and shock better than many fasteners.
- Permanent fastening - Unlike threaded fasteners, rivets form a permanent connection. The deformed rivet cannot come undone over time.
- Ease of installation - Riveting is generally quick and requires no special tools other than a riveting hammer. The installation process is simple compared to many other fastening methods.
- Variety - Rivets come in a wide range of materials, head styles, diameters, and lengths to accommodate different fabrication needs.
- No damage to materials - Riveting applies pressure evenly to compress the rivet body. It does not damage or weaken surrounding materials like drilling holes can.
- Corrosion resistance - Many rivet options provide excellent corrosion and weather resistance. Certain materials make rivets suitable for harsh environments.
- Shear strength - Rivets have high shear strength to withstand loads perpendicular to the rivet axis. The large rivet head helps distribute stresses.
Common Rivet Types for Sheet Metal
There are several types of rivets commonly used in sheet metal fabrication:
- Solid rivets - As the name suggests, these consist of solid rivet bodies. Common head styles include round, countersunk, and flat rivets. Solid rivets work for most general sheet metal fabrication.
- Blind rivets - These specialized rivets can be installed without access to both sides of a sheet. Blind rivets are inserted with access to only one side and use a stem that breaks off after forming the second head.
- Self-plugging rivets - These feature a tubular rivet body filled with a malleable alloy slug. When pressed together, the slug deforms to fill in the gap left by the mandrel. This creates a sealed rivet ideal for watertight applications.
- Drive rivets - These feature rivet bodies with pre-formed heads. Driving the mandrel up from the bottom creates the second head. Drive rivets allow riveting very thin materials.
- Split rivets - These have split tails that fold outward when compressed to create a wide second head. Split rivets are used in high vibration applications.
- Flush rivets - These have rivet bodies that are countersunk into surrounding materials so the heads sit flush with surfaces. Flush rivets create smooth outer surfaces.
Rivet Materials
Sheet metal fabricators can select rivets in an array of materials:
- Aluminum - Lightweight but strong aluminum rivets suit many fabrication projects. Aluminum provides good corrosion resistance.
- Steel - Strong, durable steel rivets work for industrial, high-stress applications. Carbon steel and stainless steel options are available.
- Copper - Ductile copper rivets form well without damage. Copper offers excellent conductivity and weather resistance.
- Monel - This nickel alloy resists corrosion and salts/acids while maintaining good strength and formability.
- Titanium - Extremely strong but lightweight titanium rivets suit demanding aerospace applications.
- Plastic - For lightweight and corrosion-resistant needs, plastic rivets like nylon and polypropylene can work.
The material must suit the sheets being riveted and the working conditions. Factors like strength needs, corrosion resistance, weight, and cost play a role in material selection.
Riveting Process
Installing rivets to join sheet metal is a relatively simple process but does require some care. Here are the basic steps:
1. Drill matching holes in the materials to be joined. Holes must be oriented across from each other with the sheets aligned.
2. Select a rivet with the proper diameter and length based on material thickness. The rivet length should match the total thickness of the materials.
3. Insert the rivet bodies into the holes with the mandrel stems still inserted.
4. Use a rivet gun or riveting hammer to upset the rivet body, spreading the tails to form the second head. This squeezes and joins the materials.
5. The mandrel stem should snap off and break free as the second head forms. Remove any remaining stem material.
6. Check that the rivet formed properly without damage and pulls the materials tightly together.
Proper hole sizes and rivet specifications must be followed to create solid joints. Riveting sheets of different thicknesses together takes some trial and error.
Rivet Hole Considerations
For good results, the rivet holes punched or drilled into the sheet metal must have the right characteristics:
- Diameter - Hole diameter should closely match the rivet shank diameter for a tight fit. Too large and the rivet may lack grip; too small can crack materials.
- Aligned - Rivet holes must directly align between mating sheets to install rivets.
- Free of burrs - Any burrs around the holes can keep materials from seating flush during riveting. Deburr thoroughly.
- Spacing - Follow recommended spacing between rivets and edges to prevent distortion. Spread rivets evenly.
- Depth - Consistent hole depth helps create uniform rivet clinching. Rivets require a minimum grip length to fasten securely.
Properly drilling or punching holes is crucial for rivets to function as intended. Consult rivet specifications to determine ideal hole placement and diameters.
Riveting Thin Metals
Joining thin sheet metals with rivets takes some care to avoid damage but can produce professional results. Here are tips for riveting thin gauge materials:
- Use smaller diameter rivets to reduce distortion around holes. Opt for rivets just large enough to clinch properly.
- Select rivets with the correct grip range for the thin materials. Use shallow semi-tubular rivets.
- Punch holes rather than drilling to minimize distortion. Fine tune punch and die clearance.
- Use smooth-faced hammers or rivet guns to upset rivets. This spreads force evenly.
- Employ rivet sets that fit the rivet head profile to direct hammer impacts.
- Rivet from the center outward and symmetrically to balance stresses.
- Install fasteners progressively, working across the materials. Allow time for metal to relax between rivets.
- Anneal or normalize metals beforehand to impart ductility that resists cracking.
- Place resilient bucking bars beneath materials to absorb and evenly spread forces.
- Consider flush rivets so rivet heads don't locally stiffen materials.
With careful tooling and techniques, even thin sheet metals can be riveted effectively. Riveting remains a go-to fastening method for sheet metal fabricators. CNC Milling CNC Machining