Riveting in Sheet Metal Fabrication(calcul coût découpe laser Gavin)
- Time:
- Click:14
- source:MAJA CNC Machining
Types of Rivets for Sheet Metal
There are several types of rivets suitable for different sheet metal fabrication applications:
- Solid rivets - These are one-piece rivets made of steel, aluminum, copper, or other metals. They are inserted through pre-drilled holes and deformed with a rivet gun or hammer to flare out the bottom shank. This securely fastens the rivet in place.
- Blind rivets - Also known as pop rivets, these have a mandrel through the center. After insertion in a pre-drilled hole, a rivet gun pulls the mandrel head to flare out the rivet body. The mandrel snaps off inside the rivet. Blind rivets are ideal for attaching sheet metal where access is only available from one side.
- Self-piercing rivets - As the name suggests, these cut their own hole rather than requiring pre-drilling. A semi-tubular rivet is forced through the top sheet, piercing the bottom layer. The tail is then flattened with a rivet gun to lock it in place. Self-piercing rivets create leak-proof joints while avoiding pre-drilling steps.
- Structural rivets - Used for high-strength structural applications, these have large head diameters and made from steel, aluminum, or specialty alloys. Structural rivets come in universal, countersunk, and various other head styles.
Rivet Joint Design
Proper rivet joint design is critical for a durable connection:
- Rivet diameter - The rivet diameter should match the sheet thickness. Larger sheets require larger diameter rivets. A good rule of thumb is rivet diameter = sheet thickness x 1.5.
- Hole diameter - Holes must be slightly larger than the rivet diameter to allow insertion. Typically ~0.1 mm larger. Too loose and the rivet won't clamp properly. Too tight can crack the sheet metal.
- Edge distance - Rivets should be placed at least 2x the rivet diameter from sheet edges. This prevents edge tearing. Closer spacing risks joint failure.
- Pitch - Rivet rows should be evenly spaced down the joint. Adjacent rivets are typically spaced 2-4x the rivet diameter. Wider pitch reduces rivet count but may compromise strength.
- Rows - Long joints require multiple rows of rivets for sufficient fastening strength. Extra rows also help mitigate alignment issues during assembly.
Riveting Process
The basic process for riveting sheet metal is:
1. Prepare materials - Shear metal sheets to size and drill holes (or use self-piercing rivets to skip this step). Deburr holes and clean surfaces.
2. Clamp and align - Clamp sheets together along the joint line using C-clamps, vise grips, or assembly jig. Align holes between layers.
3. Insert rivets - Place rivets in each hole with the rivet head against the top layer of material. Rivet length should match total material thickness.
4. Set rivets - Use a rivet gun, hammer, or rivet squeezer to deform the rivet tail. This flares the rivet and clamps sheets together. Set all rivets in a joint before releasing clamps.
5. Inspect joint - Check for proper rivet flaring and clamping. Rivets should be centered in holes without cracks in the joined materials.
Riveting Tools
Setting rivets requires force to flare the rivet body. Common riveting tools include:
- Pneumatic rivet guns - Air-powered for heavy duty riveting. Different nosepieces fit various rivet head styles. Easy to control force and speed.
- Hydraulic riveters - Use hydraulic pressure to set rivets. Allows high force in compact tools. Good for large or high strength rivets.
- Hammers - A bucking bar holds the rivet tail while the hammer deforms the head. Low cost but requires skill. Only suitable for softer materials.
- Hand squeezers - Scissor-like squeezers with concave dies to flair both rivet ends. Easy to use but limited force. Good for small or blind rivets.
Riveting Advantages
Some key benefits of riveting sheet metal versus other joining methods:
- Quick and easy - No need to pre-heat or prepare materials. Minimal equipment needed.
- Leak-proof - Rivets produce water/airtight sealed joints. Useful for enclosures, ducts, tanks, etc.
- Vibration resistant - Rivet heads dampen vibration to prevent joint fatigue and loosening.
- Doesn't weaken base metal - Unlike welding, riveting doesn't affect material strength or hardness.
- Allows dissimilar materials - Can join different metals or other materials like plastics. Just ensure proper corrosion protection.
- Easily inspected - Visually check installed rivets to ensure proper installation. Failed rivets are also obvious.
Riveting is an efficient, reliable, and versatile fastening method for sheet metal fabrication. Proper joint design, material prep, tool selection, and installation technique results in robust, long-lasting riveted connections. This simple mechanical fastening technique will continue being a go-to option for assembling sheet metal components across many industries. CNC Milling CNC Machining