Riveting in Sheet Metal Fabrication(metal finishing chart Tim)
- source:ZIEG CNC Machining
Rivets allow two or more layers of sheet metal to be securely fastened together in a way that is strong, removable, and capable of withstanding vibration and stress. They have been used for centuries in applications ranging from aircraft construction to leatherwork. Here is an overview of riveting in sheet metal fabrication:
Types of Rivets
There are several types of rivets used for different sheet metal fabrication applications:
- Solid/blind rivets - These have a pre-formed head on one end and must be set using a rivet gun or other specialized setting tool. The setting action expands the tail and clamps the rivet in place. Blind rivets come in many head styles and materials.
- Semi-tubular rivets - These have a partially hollow body and are also set with a rivet gun. The setting tool compresses the tail and expands the body diameter for clamping force.
- Self-plugging rivets - These rivets have a stem that fills the hole during setting. The stem shears off and leaves a flush surface when set.
- Drive rivets - These are solid rivets without a pre-formed head. They are set using a hammer to flare out the tail into a head shape.
- Split rivets - These rivets have a pre-cut split along the tail that causes the tail to flare outward during setting for fast blind riveting.
- Structural rivets - Extra-large rivets designed for joining structural metal components. Requires heavy duty rivet guns and dies.
- Tubular rivets - Fully hollow rivets that provide the highest shear and tensile strength for critical applications.
Some common materials used for rivets include:
- Aluminum - Lightweight, general purpose metal with good corrosion resistance. Used for aircraft and other transportation applications.
- Steel - Strong but heavier rivets. May be plated or heat treated for enhanced corrosion or temperature resistance. Common for high strength structural joints.
- Stainless steel - Offers good corrosion resistance and strength at elevated temperatures. Used in harsh environments.
- Copper - Soft, ductile material that deforms easily for flaring into a second rivet head. Common for non-critical joints.
- Monel - Nickel alloy known for corrosion resistance. Used in marine and other wet environments.
- Titanium - Very strong but lightweight rivets. Used in aircraft and high performance applications.
There are several types of tools used to insert and deform rivets for setting:
- Hand rivet guns - Pneumatic or battery powered tools that use pulling jaws to grip and set blind rivets. Available in lightweight portable models or heavy benchtop styles.
- Hammers - For setting drive rivets and some self-plugging rivets. May use special rivet shaping dolly blocks. Hammers with hollow ground faces facilitate mushrooming the rivet shank.
- Squeeze riveters - Hand operated tools with handles that allow high manual force for setting large solid rivets. Useful in field repair and maintenance.
- Impact rivet guns - Use air pressure and an impacting mass to set heavy duty pull rivets. Allows high force application.
- Orbital riveters - Rivet heads are shaped using an orbital vibrating hammering process. Produces smooth uniform head profiles.
- Automated riveting - Robotic riveting systems for mass production. Can upset multiple rivets precisely and simultaneously.
Rivet Joint Design
Proper design of the riveted joint is critical for strength and durability:
- Hole Size - Holes should be 1/16" larger diameter than the rivet shank for best results. Too tight of a fit can split the surrounding material.
- Rivet Spacing - Rivets must be spaced 3-4 diameters apart for full strength. Closer spacing reduces strength.
- Edge Distance - Rivets should be placed at least 2 rivet diameters from sheet edges. Less edge distance risks tear-out.
- Rivet Length - Thickness of stacked material should be 1.5-2x the rivet length to allow material compression and head formation.
- Row Patterns - Offset rivet rows 50% for most even load distribution. Aligning rows weakens the joint.
- Number of Rivets - More rivets provide greater total joint strength. Determine based on shear and tensile loads.
- Hole Pattern - Drill holes using templates or CNC control for consistency. Keep holes straight, round and aligned.
Riveted Joint Assembly
The process of assembling a riveted joint involves:
1. Material preparation - Shearing, cutting, machining, hole drilling, deburring and cleaning.
2. Fixturing - Clamping parts into an alignment fixture or drilling/riveting jig. Maintains hole alignment.
3. Drilling - Drilling properly sized holes in the correct locations if not pre-punched. May use drill guides.
4. Deburring - Using files or deburring tools to remove any sharp edges inside holes that can damage rivets.
5. Rivet selection - Choosing the proper rivet type and size based on the application requirements.
6. Rivet insertion - Placing the rivet tail into the aligned holes. May require temporary fasteners to hold alignment.
7. Rivet setting - Using the appropriate rivet gun, hammer, or other tool to deform the tail into a second head.
8. Inspection - Examining the joint for proper rivet formation, head shape, hole fill, and clamping.
Proper rivet selection, hole preparation, joint design, rivet setting, and inspection results in strong, reliable riveted connections able to withstand years of service. With skill and care, riveting remains one of the most adaptable and useful techniques for assembling sheet metal components across countless industries. CNC Milling CNC Machining