Riveting in Sheet Metal Fabrication(nonferrous metals Bartholomew)
- source:GAENOR CNC Machining
Advantages of Riveting
Compared to other fastening methods like welding, screwing or gluing, riveting offers several advantages that make it a popular choice for joining sheet metal:
- Speed - Riveting is generally a quick process, allowing for high volume production. The riveting process itself takes just seconds per rivet.
- Strength - Properly installed rivets form a very strong, permanent joint. The mashed rivet head anchors securely into the materials being joined.
- Disassembly - Riveted joints can be removed by drilling out the rivets, allowing parts to be disassembled and replaced if needed. This is not possible with welded or glued joints.
- No Warping - The riveting process does not apply concentrated heat like welding, avoiding potential warping or distortion of the sheet metal.
- No Finishing - Unlike screw or bolt heads, installed rivets have a smooth surface and do not require finishing work to look good aesthetically.
- Versatility - Rivets come in many materials, sizes and styles to work in almost any application. Sheet metal, aluminum, steel, plastic and more can all be riveted.
- Lower Skill - Riveting is relatively easy to learn compared to more complex techniques like precision welding. This allows more workers to rivet.
- Automation - Automated riveting systems are available to deliver speed, consistency and high volumes in manufacturing environments.
The primary downside to riveting is the need to pre-drill holes, which adds an extra step compared to simply welding or screwing materials together. Overall riveting is one of the most useful and versatile fastening solutions for working with sheet metal.
There are several different types of rivets used in sheet metal fabrication:
- Solid/Round Head - A basic rivet style with a round head. Used for general applications.
- Countersunk Head - The head is cone-shaped to sit flush in a countersunk hole, providing a smooth finished surface.
- Large Flange Head - A wide domed flange for spreading force over more material surface. Commonly used in aircraft.
- Split Rivet - Has a pre-cut split to fold as the tail mushrooms. Doesn't requireAccess hole alignment.
- Blind Rivet - Set from one side without needing backside access. Used where full access is limited.
- Self-Piercing Rivet - Can pierce and clinch in a single operation without pre-drilled holes.
- Drive Rivet - Has splines that grip in the setting tool allowing high installation force. Used where extra strength is needed.
Rivets come in many materials including aluminum, steel, copper, stainless steel, and specialty alloys like Monel or titanium. The material is chosen based on strength, corrosion resistance and appearance needs.
There are several techniques used to install rivets in sheet metal:
Hand Riveting - The traditional method using simple hand tools. Holes are drilled or punched, rivet inserted, and a bucking bar is used to deform the rivet tail. Easy at low volumes but slower for mass production.
Pneumatic Riveting - Uses compressed air and specialized power tools to quickly insert and set rivets. Allows fast, repetitive riveting for factory production.
Hydro-mechanical Riveting - A newer technology using hydraulic force to install rivets very rapidly in a continuous process, optimal for high volume manufacturing.
Box Riveting - A two operator process with access to both sides of a panel. Holes are aligned between panels, rivet inserted, and heads formed simultaneously from each side.
Self-Pierce Riveting - Uses specialty rivets that cut through the top material and mushroom into the bottom material without pre-drilling. Common in auto manufacturing.
Orbital Riveting - Uses an orbital riveting head powered by compressed air that delivers fast, uniform sets around a central axis point. Ideal for tubes and other cylindrical parts.
Underwater Riveting - Used to rivet extremely thick stacks of metal that can distort or move during riveting. Water pressure holds parts steady. Used on ships and other large structures.
Rivet Joint Design
Properly designed rivet joints are critical for strength. Factors that determine riveted joint design include:
- Rivet Diameter - Larger diameter provides greater strength to resist tearing through the hole.
- Rivet Spacing - Must be adequate spacing between rivets to distribute load. Typically 2-3 times rivet diameter.
- Edge Distance - Rivets should be placed no closer than 1.5 times the rivet diameter from sheet edges.
- Hole Fit - Holes should match rivet diameter closely for optimal fill and clamping pressure.
- Material Thickness - Thicker stacked material requires longer rivet length and more force to deform.
- Rivet Pattern - Staggering rows or using zigzag patterns optimizes joint strength. Straight rows in line with force are weakest.
Proper rivet selection, quality hole punching/drilling, and correct set pressure are also critical for achieving strong, reliable riveted joints in sheet metal assemblies. Testing of joint samples should always be done to validate designs.
When properly designed and installed, riveted joints can approach or even exceed the strength of the base materials being joined. Rivets work by clamping the materials being fastened tightly together over a large area, with the rivet shank transferring shear loads between the parts. This allows very good load distribution and resistance to failure.
The hardness and deformation of the set rivet head and tail also contribute to joint strength by anchoring the rivet solidly in place against forces trying to separate the materials. Driving the rivet shank to completely fill the hole provides added strength by maximizing clamping pressure.
Well placed rivets in shear applications can withstand tremendous loads before failing. Rivets are commonly used in high stress aircraft assemblies and other demanding applications where strength and reliability are critical.
While not quite as strong as a continuous weld joint, properly designed and installed rivet joints exhibit excellent strength for sheet metal fabrication across many industries. The versatility and reliability of riveting makes it one of the most useful processes for assembling sheet metal components. CNC Milling CNC Machining