Riveting in Sheet Metal Fabrication(machining process Sally)
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Durability - The large contact area and mechanical interlock created by rivets forms an extremely strong connection that resists vibration and shock loads better than other fasteners. This makes riveted structures ideal for applications like aircraft, bridges, and heavy machinery.
Leakproof - Unlike screws or bolts, a properly installed rivet completely fills the hole it is driven through, creating a watertight seal. This prevents leakage at the joint and corrosion between layers of sheet metal. Riveting is commonly used to fabricate tanks, ducting, and enclosures.
Efficiency - Automated riveting machines allow very high riveting rates in mass production. And unlike welding, riveting can join dissimilar metals and avoids concentrated heat effects. This speeds up assembly time and reduces distortion.
Low Cost - Rivets themselves are an inexpensive fastening component. And riveting tools have low upfront costs compared to other metal fastening equipment. The productivity and quality gains also offset riveting expenses.
There are two main types of rivets used for sheet metal fabrication:
Blind Rivets
Blind rivets, also known as pop rivets, are tubular and accessible from only one side of a joint. Holes are drilled through the top sheet(s) of metal but only partially into the bottom layer. A blind rivet is inserted into the hole and as the stem is pulled, the body expands and clamps the sheets together. The stem snaps off flush after installation. Blind rivets come in various sizes and materials like aluminum, steel, and stainless steel. They are the fastest type of rivet to install but cannot carry as much load as solid rivets.
Solid Rivets
Solid rivets are drive rivets that are hammered into place using a pneumatic rivet gun and bucking bar. Holes are drilled through all the sheets to be joined and the rivet body is placed in the hole. The gun hammer impacts the rivet head while the bucking bar supports the tail end. This deforms and flares out the body, clamping the metal layers tightly together. Solid rivets require access to both sides but make very rigid, reliable joints ideal for structural applications. Common materials include steel, aluminum, copper, and Monel.
Rivet Selection
There are several factors to consider when selecting rivets for a sheet metal fabrication project:
- Strength - The rivet needs to be strong enough to carry expected loads without failing. This depends on the material’s shear and tensile strength. Solid rivets are stronger than blind rivets.
- Sheet Thickness - Longer rivets are needed to join thicker stacks of sheet metal. They are available in many standard lengths.
- Material - Rivet material should match or be compatible with the sheets they join. This prevents galvanic corrosion.
- Surface Finishing - Some applications require rivets with decorative heads or colored finishes for aesthetics.
- Access - Blind rivets can be installed from one side. Solid rivets need access to both sides.
- Automation - Special fast-setting blind rivets are designed to feed in automated tools.
Proper Riveting Technique
Proper technique is crucial for creating secure, reliable riveted joints in sheet metal:
- Drilling - Holes must be round, clean, and match the rivet diameter closely. Uneven or oversized holes can cause joint failure.
- Alignment - Sheets must be clamped tightly together before drilling and riveting to ensure hole alignment.
- Bucking - A bucking bar needs to be held squarely on the backside when driving solid rivets.
- Setting Force - Rivets require sufficient force to deform and spread the tail without damaging the surrounding metal.
- Interference - Joint design should avoid rivets interfering with assembly components.
- Edge Distance - Rivets should be placed at least 1.5x the rivet diameter from sheet edges.
- Spacing - Rivets should be evenly spaced in staggered rows to distribute load.
- Inspection - All set rivets should be inspected for proper head formation, tight clamping, and no cracks.
Riveting Applications
Because of its versatility, riveting has many applications in sheet metal fabrication:
- Aircraft Skin - Riveting is the primary assembly method in airframe manufacturing to join fuselage skins, wings, and other components. The flush aerodynamic surface and reliable strength make rivets ideal for aviation.
- Metal Buildings - Rivets assemble the wall and roof panels of prefabricated steel buildings. The joints withstand wind, seismic activity, and snow loads.
- Truck/Trailer Bodies - Rivets help connect the side, roof, and rear panels on heavy truck and trailer bodies because of their durability under road vibrations.
- Electronic Chassis - Electronics enclosures, racks, and chassis often use small blind rivets to fasten sheet metal panels due to their speed of installation.
- Pressure Vessels - The leakproof joints formed by rivets makes them applicable for assembling tanks and pipes that need to contain high pressure fluids.
- Bridges - Structural steel girders are joined with hundreds of solid rivets on truss bridges due to their shear strength and reliability.
- Boat Hulls - Marine-grade rivets assemble sheet aluminum hull plates below the waterline because of their corrosion resistance in sea water.
In summary, riveting is a trusted and highly effective method of joining sheet metal components across many industries. Proper rivet selection and installation technique ensures tight, durable, and leakproof joints in fabricated metal structures and equipment. With the right process, rivets outperform many other mechanical fastening methods. CNC Milling CNC Machining