Riveting in Sheet Metal Fabrication(welding plastic together Buck)
- source:YESCOM CNC Machining
When to Use Rivets
Rivets are ideal for joining thin sheets of metal that would be difficult to weld or bolt together. The riveting process deforms the rivet, creating a strong clinching force that holds the metal sheets tightly together. Rivets can be used to join sheet metal up to about 1/8” thick, though thinner gauges under 1/16” are preferred. They create leak-proof joints while allowing some flexibility in the metal.
Rivets are commonly used in ductwork, gutters, electronics enclosures, automobile bodies, aircraft skins, and many other sheet metal fabrications. Almost any place where thin metal sheets need an inexpensive but sturdy fastening method, rivets do the job.
Advantages of Rivets
Compared to welding or screwing sheets together, rivets offer numerous benefits:
- Speed – Hand riveting is quick once you get the hang of it. No need for setup or slow heating/cooling. Automated pneumatic riveters are even faster.
- Cost – Rivets themselves are inexpensive, as is basic riveting equipment. Minimal training needed to start riveting.
- Strength – The compressive force of rivet setting creates joints that are as strong or stronger than welded or screwed joints.
- No Heat – The riveting process requires no heat, avoiding warping or annealing issues.
- Appearance – The smooth appearance of finished rivets is appealing on visible surfaces. Available in multiple head styles and finishes.
- Flexibility – The clinched joint allows some movement between riveted sheets. This reduces stress and potential cracks.
- Simplicity – Riveting avoids complex welding procedures or precise torque requirements of screws. Easy to learn and implement.
- Corrosion Resistance – Many rivet materials and coatings resist corrosion better than welds.
For most thin sheet metal assemblies, rivets outperform other fastening methods in terms of cost, quality, and functionality. Their flexibility, strength, and quick installation make them a staple of sheet metal shops.
Types of Rivets
While all rivets work essentially the same way, they are manufactured from different materials in a variety of head shapes and sizes. Common types include:
Aluminum Rivets – Lightweight and corrosion resistant, aluminum is suitable for many indoor and outdoor applications. Usually have a domed head.
Steel Rivets – Very strong but prone to rusting. Often have large flat heads to increase clinching power. Zinc plating improves corrosion resistance.
Stainless Steel Rivets – The ultimate in strength and corrosion resistance. More costly but ideal for harsh environments.
Monel Rivets – Nickel-copper alloy with excellent corrosion resistance. Used in marine and other wet settings.
Solid Rivets – Made entirely from the base rivet material. Requires access to both sides of the work.
Blind Rivets – Have a built-in mandrel that gets pulled to expand the rivet. Only one side access needed.
Split Rivets – Spiral split allows rivet to be expanded for tight clinch. Removes need for hammering.
Drive Rivets – Hammer-set rivets with a hollow center. Used where an unobstructed hole is needed.
Rivet size is measured by diameter (in inches or mm) and grip length. Grip is the total thickness of all materials being joined. Use a rivet grip 25-50% longer than the actual grip length for proper clinching.
Best Practices for Riveting
While riveting itself is straightforward, proper technique is needed to create lasting, leakproof, and attractive riveted joints. Keep these tips in mind:
- Hole Alignment – Matching up holes precisely is critical. Rivets can only pull sheets together rather than shifting them sideways.
- Hole Size – Clearance between rivet and hole edges should be about 1/32”. Oversized holes reduce rivet strength.
- Sheet Support – Use an anvil, buck, or other solid support while hammering. This prevents distortion.
- Hammer Choice – A lightweight riveting hammer allows quick striking without damaging rivet heads.
- Set Force – Use the recommended hammer force and number of blows to set each rivet type. Too little won't deform it enough; too much can damage the surrounding metal.
- Head Styles – Choose rivet head shape based on visibility and clinching needs. Consider countersunk in thin materials.
- Spacing – Allow 1-2 times the rivet diameter between rivets and sheet edges. More spacing on flexible or thin materials.
- Rivet Length – Only the manufactured head should protrude through the hole. Excess shank means the rivet is too long.
- Number of Hits – Set each rivet with a single confident strike of the hammer if possible. Multiple lighter hits work-harden the rivet.
- Angle – Hit rivet heads squarely when setting. Glancing blows lead to uneven deformation.
- Pressure – Lean into the hammer when striking to maximize compression force on the rivet shank.
- Inspection – Confirm the set rivet has a wide, neatly formed head and solid clinch before moving on.
Proper riveting technique comes with practice. Take your time and check each joint until you develop a feel for the process. Consistently high-quality riveted sheet metal assemblies result from patience and care with the details.
Riveting Sheet Metal with a Pneumatic Riveter
While hammer riveting works fine for occasional jobs, production shops commonly use pneumatic riveters to boost speed and consistency. These air-powered tools use an internal mechanism to quickly compress and set each rivet with pulling force that exceeds hammering. Here are some tips for riveting sheet metal with pneumatic rivet tools:
- Tool Size – Choose a riveter with sufficient throat depth for your rivets and material thickness. Too little capacity results in incomplete setting.
- Air Supply – Use the recommended air pressure for the riveter. This is usually around 90 PSI. Higher pressures stress the tool.
- Technique – Keep the gun perpendicular to the rivet head. Let the tool do the work rather than forcing it.
- Hand Position – Cup your fingers behind the mandrel exit to catch spent mandrels. Never point towards yourself or others.
- Material Support – As with hammer setting, make sure to properly support the material being riveted to avoid distortion.
- Set Confirmation – Visually check each rivet head to confirm proper setting before moving on.
- Tool Maintenance – Keep riveters well-oiled and lubricated to prevent wear, sticking, or seal failure.
- Safety – Wear eye protection, avoid awkward positions, and never point riveters at people. Be wary of sharp mandrels.
Pneumatic riveters make quick work of production jobs once dialed in. Always test settings on scrap pieces first to confirm proper clinching before riveting final assemblies. Taking a few simple precautions will lead to safe, successful automated riveting.
Rivets have been used for millennia because they offer a simple, reliable method for joining sheet metal components. Understanding the different types of rivets and following best practices for manual or pneumatic setting will produce strong, lasting sheet metal fabrications. With a little care up front and some practice, you’ll be riveting like a pro in no time. CNC Milling CNC Machining