Riveting in Sheet Metal Fabrication(brass value per pound Verne)
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Riveting offers many benefits for sheet metal assembly:
Durability and Strength - Rivets form a strong mechanical connection that has excellent resistance to vibration and shock loads. The rivet head distributes force over a larger area than other fasteners like screws.
Ease of Installation - Riveting is generally quick and easy to install with either manual or pneumatic rivet guns. It does not require threading or tapping holes like screws. Minimal access space is needed on one side.
Disassembly and Reuse - Rivets allow nondestructive disassembly for maintenance or repair. The rivets can be sheared off and replaced while reusing the existing holes. Other fasteners often damage threads during removal.
Appearance - Countersunk rivets provide a smooth finished surface. Rivet heads can be painted to match surrounding materials. The smooth surface resists dirt collection.
Rivet Types and Materials
There are two main categories of rivets: blind and solid. Blind rivets can be installed where access is only available from one side. Solid rivets require access to both sides of the assembly.
Common rivet materials include:
- Aluminum - Lightweight and moderately strong. Used for aircraft and transportation applications.
- Steel - Strong and durable but heavier than aluminum. Used for heavy machinery and structural applications.
- Monel - Corrosion resistant nickel alloy used in marine and chemical environments.
- Copper - Used for electrical conductivity in bus bars and switchgear.
- Stainless steel - Very corrosion resistant for use outdoors and in water.
Riveted Joint Design
Proper design is critical for a strong riveted joint. Some key factors include:
- Rivet diameter - Should match the sheet material thickness. Larger diameters increase shear strength.
- Hole diameter - Precision drilling avoids loose fit which reduces strength. Typically 1-2 thousandths over rivet diameter.
- Edge distance - Minimum spacing from rivet center to sheet edge. Prevents edge tearing.
- Pitch - Spacing between rivet centers in a row. Pitch determines joint flexibility.
- Row spacing - Distance between parallel rows of rivets. Staggered rows are recommended.
- Number of rivets - More rivets spread force over larger area and provide redundancy.
Riveting Process
There are several techniques used for riveting sheet metal:
Hand Riveting
The traditional method uses simple hand tools. A pneumatic bucking bar is held against the back side while the rivet gun head is formed on the front side. Hand tools require access to both sides which limits applications. Best suited for prototype and low volume production.
Self-Piercing Riveting
Blind rivets that do not require back side access. As the rivet is driven into the top sheet, the pressure causes the bottom sheet to deform, filling the rivet grooves to form a interlock. Common for automotive panels. Requires precision thickness matching.
Impact Riveting
A rivet gun with an integrated hammering function helps drive rivets into hard materials. The hammering action deforms the materials around the rivet to form a tight joint without bucking bar support. Used where back side access is restricted.
Orbital Riveting
A high speed automated process using a hydraulically driven head that orbits around the axis of the rivet, while exerting downward pressure to form the head. Produces consistent high quality results at fast rates for manufacturing.
Automated Riveting
Robotic automation with precision rivet feeding, drilling and driving allows high volume production. Automation ensures repeatability and quality while reducing labor costs. Integrates inspection systems and data collection.
Rivet Setting Force
Sufficient force must be applied to properly form the rivet head and deform the shank. Manual squeezers typically apply 5,000-15,000 lbs force. Pneumatic rivet guns supply up to 4,000 lbs. Larger shop riveters may exceed 50,000 lbs of force. Force is adjusted to the rivet diameter and material.
Inspection
Inspection procedures help identify any defects that could compromise joint integrity:
- Confirm flush rivet head against panel surface
- Check for cracked or deformed material around rivets
- Shear test sample rivets to confirm proper strength
- Confirm minimum edge distance is maintained
- Visually inspect for loose rivets or gaps in joint
Properly installed and inspected rivets will provide maximum strength and durability for sheet metal assemblies. Riveting remains a versatile, economical and highly effective fastening method. Continued technology advancements are expanding the capabilities and benefits of rivets in both manufacturing and field service applications. CNC Milling CNC Machining