Riveting in Sheet Metal Fabrication(stainless steel bending Dana)
- source:GAENOR CNC Machining
In sheet metal fabrication, riveting is commonly used to assemble parts made of thin gauge metals, such as aluminum, steel, stainless steel, and copper. It offers several benefits over other mechanical fastening methods:
- Rivets can be installed quickly with minimal equipment. A riveting hammer or rivet gun is all that's needed for most applications.
- The riveting process deforms the rivet shank, creating a wide footprint to distribute load across more material for extra strength.
- Riveted joints have good vibration resistance compared to other joining techniques.
- Installation causes work hardening which increases the strength of the materials being joined.
- Riveting is suitable for both shop environments and field work. Portability of equipment allows riveting on site or remote locations.
- It's a reliable technique proven by decades of industrial use. Riveted joints withstand corrosion, shock, and fatigue stresses well.
Common Rivet Types for Sheet Metal
There are several types of rivets designed for metal fabrication. The most popular include:
Solid/Round Head Rivets:
These feature a pre-formed domed head on one end and are driven to form the second head. They allow riveting access from one side which is useful where double-sided access is limited.
Also known as pop rivets, these have pre-formed heads on both ends. The mandrel stem is pulled to expand the rivet body behind the joint material. Easy to install in tight spaces or where visual access is restricted.
The driving force causes the rivet body to fold outward and flare against the reverse side material. Allows high clamping pressure for severely vibrating assemblies.
Extra large rivets which can fill holes up to 1 inch in diameter. Their large footprint gives excellent shear strength for heavy structures subject to dynamic loads.
Hollow with a large bearing surface area. Best where air or liquid tight sealing is needed between joints. Popular for attaching guttering components.
The rivet body is tapered to fill gaps in prepunched holes which may have become enlarged. Provides a precision fit even when hole sizes vary slightly.
Installation Tools for Sheet Metal Riveting
The most basic riveting tool is a hammer which is used to pound the rivet shank into a flare. While simple and inexpensive, hammering causes operator fatigue and inconsistency in the formed head.
Pneumatic rivet guns offer more uniform results with less effort. A hammer inside the tool is pneumatically driven to form the rivet head in seconds. Handheld squeeze models allow riveting in any orientation.
Battery powered electric tools are the most portable option. Without any air hoses to drag around, they let installers easily rivet overhead, around corners, or high up on structures. Cordless tools with lithium-ion batteries rival air tools for speed while operating quietly.
Hydraulic rivet squeezers use water pressure to advance a conical plunger. The plunger flares the rivet shank outward into the surrounding hole. Minimal heat is generated for riveting delicate materials. Pressures of 10,000 psi or higher are possible.
Automated riveting systems are used for mass production. Programmable machines position and set each rivet precisely. Multiple rivet guns can operate simultaneously to join large fabrications in minutes. Operator fatigue and variability are eliminated.
Rivet Joint Design Considerations
Proper design is key to achieving strong, long-lasting riveted connections in sheet metal assemblies. Factors which must be addressed:
- Rivet Diameter - should match the drilled hole size closely. Interference fits are recommended for high strength.
- Sheet Thickness - thicker metal requires larger diameter rivets to prevent tearing around the hole.
- Spacing - adequate margin between rivets prevents distortion. Typically 2-3 times rivet diameter.
- Edge Distance - rivets should be 1.5-2 times the rivet diameter from sheet edges. Prevents edge tearing.
- Rows - multiple rows may be needed for wide joints. Stagger overlapping rows for best load distribution.
- Materials - soft materials like aluminum require smaller rivets and tighter spacing than harder alloys.
Proper hole preparation is also vital. Drilling high quality holes prevents problems when inserting and setting the rivets. Holes should be round, concentric, and sized correctly for the rivets according to manufacturer specs. Deburring removes sharp edges which could cut rivet heads.
Riveted Sheet Metal Joint Configurations
Rivets can produce solid joints in a variety of sheet metal connection types. Common configurations include:
Lap Joints - Two overlapping sheets are drilled and riveted together. Provides good shear resistance.
Butt Joints - Sheet ends are aligned and secured with rivets in a row. Minimal material overlap.
Corner Joints - Rivets placed along folded sheet edges connect sides at 90 degree angles.
Edge Joints - Rivets installed along two matched sheet edges keep them aligned.
Patch Joints - A plate is riveted over a hole or opening to provide reinforcement.
Channel Joints - Rivets installed along the open side of a channel keep sides together.
In some cases, using solid rivets could compromise the integrity of very thin sheet metal. Fallout from the drilling process must escape somewhere. Blind rivets are recommended for these situations since they displace material inwards rather than outwards during installation.
Riveting sheet metal takes skill. Operators should be properly trained on hole preparation, rivet selection and use of tools. With practice, riveting quickly becomes a smooth process. The versatility of rivets will continue to make them a staple fastening method for sheet metal fabricators. CNC Milling CNC Machining