Riveting in Sheet Metal Fabrication(titanium vs aluminum Solomon)
- source:ZIEG CNC Machining
What is a Rivet?
A rivet is a mechanical fastener that consists of two main parts - the rivet body and mandrel. The rivet body is a head on one end and a shank on the other. The mandrel inserts into the hollow shank and is used to flare out the tip, securing the rivet in place. Once installed, the excess mandrel is broken off.
Rivets come in a variety of shapes, sizes and materials. Some common types used in sheet metalwork are:
- Solid rivets - made from a single piece of material such as aluminum or steel. Used for high strength applications.
- Blind rivets - have a built-in mandrel that doesn’t need to be removed. Used when access is only available to one side.
- Self-plugging rivets - seal the hole after installation to provide a watertight connection. Useful for electronics enclosures.
- Drive rivets - contain a tapered mandrel that is hammered rather than squeezed to flare out the rivet body.
- Structural rivets - high shear strength for connecting structural framing elements.
Benefits of Riveting Sheet Metal
There are several key advantages that make riveting a popular choice for joining sheet metal:
- Permanent - Once installed, solid rivets cannot be removed without drilling them out, creating a permanent joint.
- Vibration resistant - Rivets maintain tight clamping force between parts even when subjected to vibration.
- Cost effective - Raw rivets are inexpensive hardware items that are quick to install. Minimal tooling is required beyond a rivet gun.
- Strength - Rivets spread load across the joint and can be very strong in shear and tension. The strength depends on rivet material and size.
- No heat or sparks - The cold mechanical process of riveting avoids heat input which could warp or alter the properties of heat treated metals. It also eliminates sparks that could ignite flammable materials.
- Accessibility - Blind rivets can join layersaccessible from only one side.
- Sealing - Some rivets seal out moisture and create airtight enclosures. Self-plugging types fill the hole.
- Appearance - The smooth finished look of rivet heads can enhance the aesthetic qualities of a product.
Riveted Joint Design
Properly designed riveted joints require carefully determining the appropriate rivet size, material, spacing and layout. Factors to consider include:
- Shear strength - The thickness of the materials and required shear load capacity dictate rivet diameter and material. More rivets spread the load across a wider area.
- Spacing - Rivets must be spaced apart sufficiently to maintain joint integrity and avoid excessive material stresses between holes. Typical spacing is 2-4 times the rivet diameter.
- Edge distance - For maximum strength, rivets should be located at least 1.5 times the rivet diameter from sheet edges.
- Rows - Multiple parallel rows of rivets are staggered to distribute force effectively across the joint.
- Hole size - Holes must closely match the rivet diameter for a tight fit and good clamping pressure. Allow 10% clearance for structural rivets requiring hammering.
- Material pairing - Rivet material should match or be softer than the sheet metal to avoid embrittlement of the rivets.
Proper rivet selection, layout, and quality hole prep are critical to achieving a long-lasting, vibration-resistant joint. Consulting rivet manufacturers’ technical guides can provide recommended practices.
Installing rivets in sheet metal is a straightforward process but requires some specialized tools. The basic process involves:
1. Drilling or punching holes to the required diameter and spacing. Deburring for smooth, even hole edges.
2. Inserting the rivet and mandrel. The protruding mandrel must fit through the holes.
3. Using a rivet gun or hammer to upset the rivet body, spreading the tail to clamp materials together.
4. Removing excess mandrel stem.
Manual and pneumatic rivet guns provide the force for solid rivets. Manual tools rely on leveraged pressure from the user. Pneumatic guns use compressed air to squeeze the rivet with consistent power and speed. Automatic feeding mechanisms can supply a steady stream of rivets.
For blind rivets, handheld or benchtop setting tools draw the mandrel into the rivet body to flare it. The mandrel snaps at a break groove when the preset clamping force is achieved.
Riveting sheet metal requires care to avoid deforming or marking the material surfaces. Using backup bars or bucking bars against the backside helps absorb some of the applied pressure. Cutting off excess mandrel length also reduces deformation risk.
Riveted joints may be tested by tap testing with a hammer after installation. A ringing sound indicates a solid connection while a dull thud reveals loose rivets needing replacement. Testing sample joints under load verifies the assembly meets strength requirements.
Applications of Rivets in Sheet Metalwork
Rivets maintain their prominence in sheet metal fabrication across a wide range of industries and products, including:
- Aircraft and aerospace - Rivets are extensively used to assemble airplane fuselages, wings, and other components where vibration resistance is critical.
- Machinery - Rivets assemble crane and truck bodies, heavy equipment guards, agricultural equipment, and machinery bases where permanent sturdy construction is needed.
- Electronics - Small aluminum blind rivets assemble consumer electronics and computer cases such as routers and servers that require access from only one side.
- HVAC ducting - Special clinching rivets permanently but removably join rectangular duct sections while maintaining air tight seals.
- Building panels - Self-plugging rivets attach aluminum siding, corrugated roofing, and wall panels while sealing out moisture penetration.
- Transportation - Rivets assemble truck trailers and cargo containers subject to road stresses and loading impacts. Stainless steel rivets withstand corrosion.
- Furniture - Rivets provide high strength, permanent attachments between metal legs and frames on desks, shelving, displays and workstations.
- Signs - Small dome head rivets securely fasten metal letters and logos onto signs of all types.
For applications needing accessible, permanent and vibration-resistant joints, riveting remains a staple fastening method. As manufacturing technologies advance, the simplicity, reliability, and economy of rivets retains their place in sheet metal fabrication. Whether using manual tools or high speed automated equipment, the basic cold mechanical process of riveting continues to benefit industrial production. CNC Milling CNC Machining