How To Rivet Sheet Metal
Content Menu
● Advanced Riveting Techniques
● Design Considerations for Riveted Joints
● Design Considerations for Riveted Joints (Continued)
● Q&A
What is Sheet Metal?
Sheet metal refers to thin, flat pieces of metal formed through industrial processes. Manufacturers create these versatile materials by shaping metal into sheets with uniform thickness, typically ranging from 0.006 to 0.25 inches (0.15 to 6.35 mm). The resulting material serves as a fundamental building block across numerous industries, from aerospace to consumer appliances. Sheet metal can be cut, bent, punched, and joined to create complex structures and components.
Common sheet metals used in riveting applications include various grades of steel, aluminum alloys, copper, brass, and titanium alloys. Each material offers distinct properties suitable for different applications. For example, aluminum alloys provide excellent strength-to-weight ratios ideal for aerospace applications, while stainless steel offers superior corrosion resistance for outdoor installations and food processing equipment.
The manufacturing process for sheet metal typically involves rolling mills that compress metal ingots to the desired thickness. Additional processing may include heat treatment, surface finishing, and other operations to achieve specific mechanical properties. Understanding these properties is crucial when designing riveted connections, as they directly impact joint strength and durability.
Rivet Basics and Functionality
A rivet is a mechanical fastener consisting of a smooth cylindrical shaft with a preformed head on one end. During installation, the opposite end (often called the “tail”) undergoes deformation to create a second head, forming a permanent connection between the joined materials. This process, known as “upsetting” or “bucking,” locks the materials together without threads or adhesives.
Unlike temporary fasteners such as screws and bolts, rivets create permanent joints that cannot be disassembled without destroying the fastener. This permanence offers exceptional reliability in applications where vibration or cyclic loading might loosen threaded fasteners over time. Additionally, the cold-forming process used in most riveting applications avoids the heat-affected zones and potential distortion associated with welding.
Rivets transfer loads primarily through shear across the shaft and bearing pressure between the rivet and the material being joined. This mechanical connection makes rivets particularly effective in applications where materials experience vibration, thermal cycling, or dynamic loading conditions.
Types of Rivets for Sheet Metal Applications
Several rivet types exist for sheet metal applications, each designed for specific joining requirements:
Solid Rivets: These represent the oldest and most reliable rivet type, consisting of a solid shaft with a preformed head. During installation, a bucking bar placed against the tail end receives impact force from a rivet gun applied to the head, deforming the tail into a second head. While requiring access to both sides of the joint, solid rivets provide exceptional strength and reliability, making them standard in critical aerospace structures and high-load applications.
Blind Rivets (Pop Rivets): Featuring a hollow body with a mandrel running through the center, blind rivets revolutionized assembly by enabling installation from just one side of the joint. When the installation tool pulls the mandrel, it deforms the blind side of the rivet before breaking off at a predetermined point. This accessibility makes blind rivets ideal for enclosed structures, tubes, or applications where back-side access is impossible.
Semi-Tubular Rivets: These combine aspects of solid and blind rivets, having a partially hollow end that requires less force to deform while maintaining excellent strength. The partial hole in the tail end facilitates controlled deformation during setting, creating consistent head formation with less installation force than solid rivets.
Drive Rivets: Featuring a grooved mandrel that spreads the rivet body when driven in, drive rivets require only hammering for installation. This simplifies the process while still creating permanent connections. They’re commonly used in applications where specialized installation tools aren’t available or practical.
Clinch Rivets: Used in specialized clinch riveting processes, these create enhanced mechanical interlocks between sheets. The technique combines material deformation with a supplemental rivet, often resulting in stronger connections than standard riveting alone.
The Riveting Process
Hole Preparation Process
Proper hole preparation forms the foundation for strong, durable riveted joints:
Drilling: Create holes through the materials to be joined, ensuring they’re slightly larger than the rivet diameter—typically 0.004″ to 0.006″ larger. For example, a 1/8″ (3.2mm) rivet usually requires a 9/64″ (3.6mm) hole. This clearance allows for thermal expansion and facilitates rivet insertion while being small enough to ensure proper head formation.
In industrial settings, CNC drilling or punching machines create precise holes with consistent spacing and edge distance. For example, aerospace manufacturers use multi-spindle drilling machines that simultaneously create perfectly aligned holes through multiple layers of material, ensuring perfect alignment for subsequent riveting operations.
Alignment: Proper alignment of holes between all layers is critical for joint strength and appearance. In aerospace applications, technicians often use temporary fasteners (clecos) or alignment pins to maintain precise registration during the riveting process. For instance, when assembling aircraft fuselage sections, hundreds of clecos might hold components in perfect alignment before permanent rivets are installed.
Deburring: After drilling, all holes must be deburred to remove sharp edges that could interfere with proper rivet setting or create stress concentrations. This critical step prevents microscopic cracks from forming around the hole edge during service. In high-precision applications, specialized deburring tools create a small radius on the hole edge, significantly improving fatigue resistance.
Countersinking: For flush applications where rivet heads must not protrude above the surface, countersinking creates an angled recess matching the rivet head angle (typically 100° or 120°). Aircraft skin joints often use countersunk rivets to maintain aerodynamic smoothness, with countersink depths precisely controlled to ensure proper rivet head seating without excessive material removal.
Rivet Selection and Preparation
Selecting the appropriate rivet involves considering several key factors:
Material Compatibility: The rivet material should be compatible with the sheet metals being joined to prevent galvanic corrosion. For example, aluminum rivets work well with aluminum sheets, while stainless steel rivets may be needed for stainless components. In marine environments, silicon bronze or monel rivets often connect aluminum components, offering excellent corrosion resistance despite the dissimilar metal combination.
Grip Range: Select rivets with the appropriate grip range for your total material thickness. The grip range indicates the combined material thickness the rivet can properly join. For instance, when connecting two 1/16″ aluminum sheets, you’d need a rivet with a grip range encompassing 1/8″ (0.125″). Using a rivet with too short a grip range results in incomplete setting, while too long a grip range may prevent proper head formation.
Diameter: Rivet diameter significantly affects joint strength and should be appropriate for the application’s load requirements. In structural applications, engineers often specify a rivet diameter at least three times the thickness of the thinnest sheet. For example, joining 0.040″ aluminum sheets might require 1/8″ diameter rivets to provide adequate strength.
Head Style: Different head styles serve specific functions:- Universal (round) heads provide maximum bearing area and are commonly used where appearance isn’t critical- Countersunk heads create flush surfaces necessary for aerodynamic or aesthetic applications- Modified heads such as brazier or mushroom offer specialized profiles for specific applications such as increased shear strength or lower profiles
For example, aircraft manufacturers use flush countersunk rivets on exterior surfaces for aerodynamic performance, while using universal head rivets internally where drag isn’t a concern.
Insertion and Setting Techniques
The insertion and setting process varies by rivet type:
For Solid Rivets:1. Insert the rivet through aligned holes with the manufactured head facing the most visible or accessible side2. Place a bucking bar against the tail end3. Apply force to the manufactured head using a pneumatic hammer or rivet gun4. The transmitted force deforms the tail into a shop head, typically 1.5 times the rivet diameter in width
In aircraft assembly lines, two technicians often work together—one operating the rivet gun on the head side and another holding the appropriately shaped bucking bar against the tail. This human coordination creates consistent, high-quality connections across thousands of fasteners per aircraft.
For Blind Rivets:1. Insert the rivet assembly (body with mandrel) into the pre-drilled hole until the rivet head seats firmly against the material surface2. Place the rivet gun over the mandrel3. Activate the gun, which pulls the mandrel4. The mandrel head deforms the rivet body on the blind side5. Continued pulling breaks the mandrel at a predetermined point
Modern automotive assembly lines use automated blind riveting systems that install dozens of rivets per minute while monitoring installation parameters to ensure quality. These systems often integrate with robotic assembly cells that position components, drill holes, and install rivets in a continuous automated process.
For Rotary Rivets:1. Insert the rivet through the prepared holes2. The rotary riveting tool contacts the rivet head3. Rotation of the tool applies even pressure in all directions4. The rivet material flows to form the shop head
This technique offers advantages for thin materials, creating less impact stress while forming consistent heads. Appliance manufacturers often use rotary riveting for attaching handles to refrigerator doors, where appearance and reliability are equally important.
Tools and Equipment
The riveting process employs various specialized tools:
Manual Rivet Guns: Hand-operated tools for setting blind rivets in small-scale applications or field repairs. A sheet metal repair technician might use a manual rivet gun to replace damaged rivets on equipment housings during on-site maintenance.
Pneumatic Rivet Guns: Air-powered tools that provide consistent force for setting rivets in production environments. These tools typically operate at 90-100 PSI and deliver controlled impact force to form solid rivet heads or pull blind rivet mandrels. Aircraft manufacturers use specialized pneumatic rivet guns with various nose pieces designed for different rivet sizes and access conditions.
Hydraulic Riveting Machines: Used for high-strength applications in industries like aerospace and construction, these machines provide precisely controlled force for large-diameter rivets. Bridge construction might employ hydraulic riveters for structural connections requiring thousands of pounds of setting force.
Bucking Bars: Solid metal blocks used as a reaction surface when setting solid rivets. Available in various shapes for different access conditions, these precision-ground tools typically weigh 2-5 pounds. The mass and shape of the bucking bar significantly influence rivet formation quality.
Rivet Squeezers: C-shaped tools that compress both ends of a solid rivet simultaneously, ideal for accessible joint locations. Sheet metal fabrication shops use squeezers for consistent results on production runs, as they eliminate the coordination required between rivet gun and bucking bar operators.
Automated Riveting Systems: Computer-controlled systems that handle multiple steps in the riveting process. Boeing’s Fuselage Automated Upright Build (FAUB) system, for example, automatically positions, drills, and installs thousands of rivets in aircraft sections with minimal human intervention, ensuring consistent quality while significantly reducing labor requirements.
Advanced Riveting Techniques
Rotary Riveting Technique
Rotary riveting forms the shop head through controlled deformation rather than impact:
The process begins with standard hole preparation and rivet insertion, but diverges significantly during the setting phase. Instead of using impact force, a rotary riveting tool spins at high speed (typically 2,000-5,000 RPM) while applying controlled pressure. This rotation causes the rivet material to flow plastically, forming a consistently shaped head.
For example, in household appliance manufacturing, rotary riveting secures internal components where consistent appearance and reliable performance are equally important. The process allows for high production speeds with minimal noise compared to impact methods. A refrigerator manufacturing line might use multiple rotary riveting stations to attach hinges, handles, and internal components at rates exceeding 1,000 rivets per hour.
The key advantages include reduced noise (crucial for factory environments), consistent head formation regardless of operator skill, and reduced stress in surrounding materials. This makes rotary riveting particularly suitable for thin materials that might deform under impact methods. Electronics manufacturers often choose rotary riveting for attaching components to thin enclosures where material distortion would be unacceptable.
Advanced rotary riveting systems include pressure and rotation monitoring to ensure consistent quality. For instance, medical device manufacturers use validated rotary riveting processes with real-time monitoring to attach components in implantable devices, where failure is not an option.
Clinch Riveting Technique
Clinch riveting combines material deformation with mechanical fastening:
This hybrid technique creates interlocked joints between sheet metals, with or without an additional rivet. Special tooling deforms the materials to create a mechanical interlock, and when a rivet is included, it reinforces the connection.
The process begins with positioning the sheets between specially designed punches and dies. When force is applied, the material flows to create an interlock. According to experimental studies, adding a rivet to the clinching process can increase the neck thickness parameter by up to 212% and the undercut parameter by 58%, significantly enhancing joint strength.
Automotive manufacturers have embraced clinch riveting for joining dissimilar materials. For example, when assembling body structures that combine aluminum and steel components, traditional welding presents challenges due to the different melting points and thermal properties. Clinch riveting creates strong connections without the metallurgical issues associated with welding dissimilar metals.
The technique shows particular advantages for materials like aluminum alloy 5754, where testing demonstrates significant improvements in joint parameters compared to standard clinching. However, the process requires higher forming forces—up to 290% greater than standard clinching for some material combinations.
Automated Riveting Systems
Automation has revolutionized industrial riveting processes:
Modern automated systems combine multiple operations in a synchronized process. For example, Airbus employs robotic riveting systems that automatically drill, clean, and install fasteners in aircraft wings, maintaining positioning accuracy within 0.005″ across components measuring over 100 feet.
These systems typically incorporate:
Computer-Controlled Positioning: CNC technology positions rivets with precision measured in thousandths of an inch. The system uses 3D model data and real-time position feedback to place fasteners exactly where specified, compensating for material variations and thermal expansion.
Multi-Head Installations: Advanced systems can install multiple rivets simultaneously, dramatically increasing production rates. Automotive assembly lines use multi-head riveters that install up to 12 rivets in a single operation when attaching body reinforcements.
In-Process Quality Monitoring: Sophisticated systems monitor installation parameters in real-time, ensuring proper rivet formation. These systems measure setting force, displacement, and sometimes ultrasonic feedback to verify proper rivet formation, automatically flagging any rivets that fall outside specified parameters.
Automated Material Handling: Complete systems incorporate component positioning, clamping, and transportation integrated with the riveting process. Aircraft fuselage assembly systems might employ massive positioning fixtures that hold components to within 0.020″ of theoretical position while automated riveting systems install thousands of fasteners.
For example, the Global Hawk unmanned aircraft manufacturing incorporates fully automated riveting systems that handle the entire process—from drilling precise holes to installing the rivets—with minimal human intervention. These systems reduce variation, increase production rates, and maintain consistent quality across all airframes.
Design Considerations for Riveted Joints
Joint Design
The configuration of riveted joints significantly impacts performance:
Lap Joints: The simplest design, where sheets overlap and are riveted together. While easy to fabricate, stress distribution isn’t optimal, with stress concentrations occurring near the edges of the overlap. In aircraft fuselage construction, manufacturers often use multiple-row lap joints with carefully calculated rivet patterns to distribute loads evenly. For example, Boeing 737 fuselage sections use three-row lap joints with staggered rivet patterns to optimize load transfer while minimizing fatigue concerns.
Butt Joints: In this configuration, sheets meet edge-to-edge with a strap (or straps) riveted over the seam. Bridge construction frequently employs butt joints with cover plates on both sides (double-strap butt joints) to maintain alignment while handling tensile loads. The Golden Gate Bridge’s original construction used tens of thousands of hot-driven rivets in butt joints connecting the massive steel plates of the suspension towers.
Corner Joints: Used where sheets meet at an angle, often with additional reinforcement. HVAC ductwork corners typically use corner joints with closely spaced rivets to prevent separation under pressure. A standard commercial air handling unit might incorporate hundreds of riveted corner joints in its sheet metal construction.
Single vs. Multiple Row Designs: Critical applications often use multiple rows of rivets to distribute load and provide redundancy. Aerospace engineers calculate optimal rivet patterns using finite element analysis and fatigue models. Commercial aircraft fuselage lap joints typically feature three or more rows of rivets in a staggered pattern to optimize stress distribution and provide fail-safe characteristics.
The restoration of vintage aircraft demonstrates the enduring effectiveness of well-designed riveted joints. When restoring a WWII-era DC-3, technicians carefully document and reproduce the original lap joint configurations, maintaining both historical accuracy and proven structural integrity that has demonstrated reliability over decades of service.
Edge Distance and Spacing Requirements
Proper placement of rivets relative to material edges prevents failures:
Minimum Edge Distance: Generally, rivets should be placed at least 2-2.5 times their diameter from any edge to prevent tear-out. For a 1/8″ rivet, this means at least 1/4″ to 5/16″ from the edge. Testing shows that placing rivets too close to edges dramatically reduces joint strength—in some cases by more than 50% compared to properly spaced connections.
End Distance in Load Direction: When load is applied parallel to the edge, greater distances may be required. In structural steel connections, end distance is often specified as at least 1.5-2 times the rivet diameter to prevent progressive failure under load. Bridge girder connections might specify end distances of 2D (where D is the rivet diameter) to ensure adequate material remains to resist tear-out under dynamic loading.
Rivet Pitch (Distance Between Rivets in a Row): Typically 3-4 times the rivet diameter for optimal strength without excessive material weakening. Too close spacing can weaken the material through multiple holes, while too wide spacing may allow excessive local deformation. Aircraft wing skin connections might use 4D spacing for 1/8″ rivets, resulting in rivets placed approximately 1/2″ apart in rows.
Gage (Distance Between Rivet Rows): Usually 2.5-3.5 times the rivet diameter, balancing material strength with load distribution. Commercial aircraft structures often use staggered patterns with calculated gage distances to optimize fatigue resistance. A typical fuselage lap joint might use a gage of 3D with rivets in adjacent rows offset by half the pitch distance.
Design Considerations for Riveted Joints
Material Selection and Compatibility
Choosing the right materials for both the rivets and the sheet metal is crucial:
Material Compatibility: Ensure that the rivet material is compatible with the sheet metals being joined to prevent galvanic corrosion. For instance, using aluminum rivets with aluminum sheets or stainless steel rivets with stainless components is common practice. In marine environments, silicon bronze or monel rivets are often used to connect aluminum components, providing excellent corrosion resistance despite the dissimilar metal combination.
Material Properties: Consider the strength, ductility, and fatigue resistance of both the rivet and sheet metal. Aerospace applications frequently use high-strength aluminum alloys (e.g., 2024-T3) for both rivets and sheet metal to maximize strength-to-weight ratios. In contrast, construction projects might use steel rivets with steel sheets for their high strength and durability.
Fatigue and Stress Analysis
Riveted joints are subject to fatigue under cyclic loading:
Fatigue Life Prediction: Engineers use finite element analysis and fatigue models to predict the lifespan of riveted joints under various loading conditions. For example, in aircraft design, engineers simulate the stress cycles experienced by riveted joints during flight maneuvers and landing cycles to ensure they meet safety standards.
Stress Concentration Factors: Rivet holes can act as stress concentrators, potentially leading to material failure. Designers often use stress concentration factors (SCFs) to account for these effects. In bridge construction, SCFs are critical in calculating the maximum allowable stress in riveted connections under dynamic loads.
Safety and Quality Control
Safety Precautions
Riveting involves several safety considerations:
Personal Protective Equipment (PPE): Always wear safety glasses, gloves, and ear protection when operating riveting tools. In industrial settings, technicians must also wear steel-toed boots and high-visibility vests to prevent accidents.
Tool Maintenance: Regularly inspect and maintain riveting tools to prevent malfunction. For instance, pneumatic rivet guns should be checked for air leaks and worn parts, while bucking bars should be inspected for damage or excessive wear.
Work Environment: Ensure a clean, well-lit workspace to prevent accidents and improve visibility. In assembly lines, workstations are often designed with ergonomic considerations to reduce fatigue and enhance productivity.
Quality Control Measures
Implementing quality control measures ensures consistent joint quality:
Visual Inspection: Regularly inspect rivets for proper head formation, alignment, and absence of defects. In aerospace manufacturing, technicians use magnifying glasses or optical comparators to verify rivet quality.
Ultrasonic Testing: Use ultrasonic testing to verify rivet integrity and detect any defects. This method is particularly useful for inspecting blind rivets where visual inspection is not possible.
Statistical Process Control (SPC): Implement SPC to monitor and control the riveting process, ensuring that parameters like setting force and rivet displacement remain within specified limits. Automotive manufacturers use SPC to monitor rivet installation parameters in real-time, automatically adjusting the process if deviations occur.
Case Studies and Examples
Aerospace Industry
In aerospace, riveting is critical for structural integrity:
Boeing 787 Dreamliner: The aircraft’s fuselage is constructed using advanced automated riveting systems that ensure precise positioning and quality control. The use of advanced materials like carbon fiber reinforced polymers (CFRP) requires specialized riveting techniques to maintain structural integrity while minimizing weight.
Lockheed Martin F-35 Lightning II: The fighter jet’s airframe incorporates thousands of rivets, with each joint carefully designed and tested for strength and durability. The F-35′s advanced materials and complex geometry require sophisticated riveting techniques to ensure reliability under extreme flight conditions.
Automotive Industry
Automotive manufacturing relies heavily on riveting for body assembly:
Tesla Model S: The vehicle’s body structure uses a combination of welding and riveting to join aluminum components. Advanced automation systems ensure precise rivet placement and quality, contributing to the car’s lightweight yet robust construction.
Ford F-150: The pickup truck’s body is assembled using a mix of welding and riveting, with rivets providing additional strength in critical areas like door hinges and roof supports. The use of high-strength steel and advanced riveting techniques enhances the vehicle’s durability and safety.
Conclusion
Riveting sheet metal remains a fundamental technique in manufacturing engineering, offering reliability, versatility, and strength across various industries. From traditional solid rivets to advanced blind and clinch riveting methods, each technique provides unique advantages for different applications. By understanding the principles of rivet selection, hole preparation, and joint design, engineers can optimize their riveting processes to meet specific performance requirements. As technology continues to evolve, automated systems and advanced materials will further enhance the efficiency and quality of riveted joints.
References
-
Study on Sheet Metal Riveting Processes and Devices, Scientific.Net, August 2013,
Key Findings: The article discusses various methods and tools used in sheet metal riveting, highlighting the importance of riveting processes in achieving desired outcomes.
Methodology: The study reviews current trends and developments in sheet metal riveting, focusing on rivet riveting and riveting without rivets.
Citation: pp. 413-416, https://www.scientific.net/AMR.753-755.413 -
Mechanical Joining of Steel Sheets in Automotive Industry, Acta Mechanica Slovaca, 2014,
Key Findings: The article explores clinching and clinch-riveting processes for joining steel sheets, highlighting their efficiency and mechanical properties.
Methodology: Experiments were conducted using different steel sheet combinations to evaluate the strength of clinched and clinch-riveted joints.
Citation: pp. 172-180, https://www.actamechanica.sk/pdfs/ams/2014/03/01.pdf -
Rivet, Wikipedia,
Key Findings: Provides an overview of rivets, including their history, types, and installation methods.
Methodology: N/A
Citation: https://en.wikipedia.org/wiki/Rivet -
Clinching, Wikipedia,
Key Findings: Discusses the clinching process, its advantages, and applications.
Methodology: N/A
Citation: https://en.wikipedia.org/wiki/Clinching
Q&A
1. What are the primary types of rivets used in sheet metal applications? – Solid, blind, semi-tubular, drive, and clinch rivets are commonly used.
2. How do you ensure proper hole preparation for riveting? – Drilling precise holes slightly larger than the rivet diameter, followed by deburring to remove sharp edges.
3. What is the purpose of using bucking bars in solid rivet setting? – Bucking bars provide a reaction surface to help form the shop head during rivet setting.
4. Can blind rivets be used in applications requiring high strength? – While blind rivets are versatile, solid rivets generally offer higher strength due to their solid construction.
5. What are the benefits of automated riveting systems? – Automated systems provide consistent quality, increased production rates, and reduced labor requirements.