Riveting in Sheet Metal Fabrication(car screws Leo)
- 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 rivet is inserted through holes in the materials being joined. The tail end is then flattened into another head with the use of a hammer or rivet gun. This creates a permanent joint by cold working and deforming the rivet.
Rivets come in a wide variety of materials, sizes and types to suit different applications. Common materials include aluminum, steel, copper and Monel. Popular types of rivets include blind, structural, drive and tubular rivets. Sizes range from 1/16 inch up to 3/8 inch in diameter. The material, type and size are selected based on the sheet metal gauge, joint strength requirements and assembly method.
Advantages of Riveting
Riveting offers many benefits that make it a popular joining method for sheet metal:
- Strong and permanent - Rivets produce joints as strong or stronger than the parent material when installed correctly. The joints do not come loose over time.
- Vibration resistant - Riveted joints can withstand vibration and shock better than many mechanical fasteners due to the wide clamping area.
- Allows flexibility - Rivets allow the joined parts to shift slightly over time as materials expand and contract. This prevents cracking.
- Works on overlapping or open joints - Rivets can join materials that are only overlapping or have open joints up to 1/8 inch gap.
- Quick installation - Riveting is relatively fast compared to welding or adhesives. Minimal surface preparation is required.
- Lower cost - Rivets are inexpensive compared to welding sheet metal together. Minimal equipment and training is required.
- Easy inspection - Installed rivets are easy to visually inspect for quality unlike welds and adhesives. Missing or poorly formed rivets can easily be identified.
Riveting Methods for Sheet Metal
There are several techniques used to install rivets to join sheet metal depending on the application requirements:
- Hammer riveting - A bucking bar holds the rivet tail stationary while the head is manually hammered to form. Best for one-off jobs.
- Pneumatic riveting - Uses compressed air to automate hammering the rivet head. Allows faster production riveting.
- Hydraulic riveting - Powerful hydraulic rams form the rivet head instead of hammering. Enables high strength and speed.
- Self-piercing rivets - Mechanically punched rivets that pierce and join metals in a single operation. No pre-drilling required.
- Blind rivets - Tubular rivets installed with only one accessible side. Common for field repairs and assemblies.
For production sheet metal fabrication, pneumatic rivet guns are the most common installation method. They strike the rivet head at up to several blows per second to quickly form strong, consistent joints. Automated riveting machines with programmable gang heads can install many rivets simultaneously over an entire part.
Riveted Joint Design
Proper joint design is crucial for rivets to create strong, lasting bonds:
- Hole size - Holes must match the rivet diameter within a tight tolerance, generally +/- 0.002 inches. Undersized holes can crack the material while oversized holes reduce strength.
- Hole spacing - Holes must have adequate material between them to prevent tearing. Typically at least 2 times the hole diameter.
- Edge distance - Holes must be a minimum distance from sheet edges, usually 1.5 times the hole diameter, to avoid edge tearing.
- Hole alignment - Any mismatch between holes can cause joint failure when loaded. Pins help align parts.
- Clamping pressure - Joint surfaces should be held tightly together while riveting to maximize strength. Clamps, pins or presses apply pressure.
- Rivet length - Should fill 85-95% of the total grip length through all materials for proper deformation.
Proper design combined with quality rivets and installation results in leak-free joints that can last the lifetime of the product.
Riveting Applications in Sheet Metal
Rivets are commonly used to assemble sheet metal parts in a wide range of products, including:
- Aircraft and aerospace - Rivets are extensively used in airframe skins and assemblies due to their vibration resistance. Common in fuselages, wings and engine nacelles.
- Metal building products - Rivets assemble sheet metal roofing, siding, gutters, downspouts, framing and more. Allow for expansion and contraction.
- Electronics enclosures - Rivets provide durable, EMI-resistant joints for sheet metal electronic chassis, racks and enclosures.
- Appliances - Sheet metal appliances use rivets to join external skins and internal compartments in ovens, washers, driers and refrigerators.
- HVAC ducting - Rivets create air-tight and strongly reinforced joints in sheet metal ducting and vents used in HVAC systems.
- Furniture - Rivets assemble enclosures, legs, braces and frames made from sheet metal in filing cabinets, lockers, carts and shelving.
- Automotive assemblies - Rivets join stamped sheet metal parts in body panels, wheels, undercarriages, engine bays and interiors.
Nearly any product built from sheet metal fabrication can benefit from riveted joints for cost-effective and durable construction. Properly installed rivets outperform most other mechanical fastening methods for sheet metal applications. With the right joint design and quality rivets, manufacturers can achieve leak-proof, vibration-resistant and long-lasting riveted assemblies. CNC Milling CNC Machining