Riveting in Sheet Metal Fabrication(90 degree gears Dinah)
- source:GAENOR CNC Machining
What is a Rivet?
A rivet is a mechanical fastener that consists of two main parts - a smooth cylindrical shaft and a head. The shaft is inserted into pre-drilled holes in the materials being joined. The rivet is then deformed to create a second head, clamping the materials together. The force created flares the rivet shaft and upsets the rivet head, creating a strong joint.
Rivets come in a variety of sizes and materials to suit different fabrication needs. Common materials include aluminum, steel, copper, and stainless steel. The material and hardness selected will depend on the type of metals being joined and the strength required.
Types of Rivets for Sheet Metal
There are several types of rivets suitable for joining sheet metal:
- Solid/Round Head Rivets: As the name suggests, these have a solid rounded head. They are one of the most common rivets for sheet metal work.
- Countersunk Head Rivets: These rivets have a flat, countersunk head that sits flush with the surface of the metal. This gives a smooth finish.
- Large Flange Rivets: These have a wide flange under the head, distributing force over a larger area for extra strength.
- Split Rivets: Also known as blind rivets, these are tubular with a mandrel through the center. When the mandrel is drawn into the rivet, it flares the tubular shaft to clamp materials. No access to both sides is needed.
- Drive Rivets: These have small centers that can be driven to flare the rivet. Often used where appearance is important.
- Structural Rivets: Designed for joining structural and load-bearing materials. They have high shear and tensile strength.
Choosing the right rivet style will depend on the specific metals, how they are oriented, and the forces they will need to withstand. Consulting a fastener supplier is recommended to select suitable rivets.
Rivet Joint Design Considerations
Properly designed rivet joints will withstand shear and tensile loads while retaining some flexibility. Here are some key factors to consider:
- Drilling Accuracy: Holes must be aligned precisely between both sheets of metal for the rivet to fit through cleanly. Any distortion can compromise strength.
- Hole Size: Clearance between the rivet and the hole is important. Too tight and the rivet won't go through. Too loose and the joint will be weak and loose. Standard clearance is 1% of the rivet diameter.
- Rivet Spacing: Rivets along a seam should be spaced 3-4 times the rivet diameter apart for optimal strength. Edge distance from the nearest rivet hole should be at least 1.5 times the rivet diameter.
- Rivet Strength: Select rivets stronger than the sheets being joined. Softer rivets may deform instead of flaring the surrounding metal.
- Number of Rivets: More rivets spread force over a larger area. Use enough to withstand expected loads.
- Materials: Choose rivets made of a similar or harder material than the components to be joined.
Following best practices for rivet joint design will result in professional quality sheet metal assemblies.
The Riveting Process
Installing rivets to assemble sheet metal components involves a few key steps:
1. Cutting - Sheets are cut to required sizes and shapes. Holes are created for rivets.
2. Drilling - Components to be riveted are clamped together and holes are drilled through all layers using a drill press. A backing plate prevents burrs.
3. Deburring - Any burrs or jagged edges are removed from the holes.
4. Aligned - Sheets are aligned and clamped in position, with rivets inserted in each hole.
5. Riveting - Special tools flare each rivet tail, upsetting the rivet head and clamping the sheets together.
6. Inspecting - The joint is checked for tightness. Minor adjustments can be made by further flaring the rivet.
7. Finishing - Excess rivet length is ground flush for a smooth finish.
The right tools and techniques make riveting sheet metal efficient and effective. With practice, you can create perfect riveted assemblies.
Riveting Tool Options
To flare rivets and assemble sheet metal, you need the proper riveting tools. Here are some of the most common options:
- Hand Riveters - Best for light duty work, these simple squeezers flare the rivet with leveraged hand pressure.
- Pneumatic Rivet Guns - Rivets are upset using compressed air. Allows high force application for heavy duty rivets.
- Battery Operated Rivet Guns - Cordless electric tools offer portable flexibility. Different nose pieces suit various rivets.
- Hydraulic Riveters - Hydraulic power provides very high pressure for large structural rivets. Used on bridges, towers, and heavy equipment.
- Accessory Tools - Sets, headers, bucking bars, and fastener holders help position and insert rivets during assembly.
Select riveting tools sized for the shank diameter of the rivets you'll be using. Proper pressure is needed to fully flare the tail without damaging the surrounding materials. Investing in quality tools will make your riveting jobs smoother.
Riveting Technique Tips
With the right tools on hand, follow these technique tips to create secure riveted joints:
- Use backing plates when drilling holes to prevent deformation and burrs. Clamp sheets together while drilling.
- Clean and deburr all holes before riveting to allow rivets to slide through freely.
- Apply masking tape strips along seams to hold rivets in alignment when inserting.
- Use adequate pressure to completely flare rivets. Rivets should be snug but not distort the metal.
- Start riveting in the middle of a seam, working out towards edges to draw materials together.
- For countersunk rivets, use a rivet set tool to form the flush head profile.
- Inspect finished rivets. Tighten any loose rivets with additional flaring if needed.
- Grind any excess shank length near flush for a clean look. Avoid overheating.
- Seal surfaces with paint or powder coat after riveting to prevent corrosion.
Mastering proper riveting technique results in professional quality finished products that will withstand daily use.
When to Choose Riveting
Riveting is an extremely versatile metal fastening method. Here are some of the advantages that make riveting a popular choice for many sheet metal fabrication projects:
- Rivets create permanent, rigid joints - Unlike welding, the joint is not a seamless bond. The mechanical interlock retains flexibility.
- Installation is quick and requires no curing time or cooling. The joint is instantaneously strong.
- Minimal surface preparation is needed compared to welding or bonding. Just drill and deburr holes.
- Riveting avoids concentrated heat effects of welding, preventing warping.
- Joints can accommodate some movement or vibration without failing.
- Riveted panels are easier to replace than welded parts if damaged. Just drill out old rivets.
- Riveting produces a professional finished appearance, especially with flush rivets.
- Most riveting can be done with simple hand tools or air riveters. Minimal investment in equipment.
For long-lasting sheet metal assemblies able to withstand daily wear and tear, riveting is the preferred joining method. With an understanding of the riveting process, you can fabricate high-quality metal components. CNC Milling CNC Machining