Riveting in Sheet Metal Fabrication(brass versus bronze Mandel)
- source:YESCOM CNC Machining
What is a Rivet?
A rivet is a mechanical fastener consisting of a cylindrical shaft and head. The shaft is inserted through pre-drilled holes in the materials being joined. The excess shaft length is then flattened into another head with force. This creates a permanent connection.
Rivets are available in many materials, sizes, shapes, and styles. Common materials include aluminum, steel, stainless steel, copper, and Monel. They range in diameter from 1/16 to 3/4 inches. Rivet shapes can be round, flat, countersunk, or brazier (domed) head. Styles include solid, semi-tubular, blind, and drive rivets. The combination of attributes makes rivets highly versatile for various sheet metal uses.
Benefits of Riveting
Rivets offer unique benefits for joining sheet metal:
- Strong and permanent - The flattening/swaging process work-hardens the rivet shank, creating a tight joint that resists vibration and shock loads. Rivets won't come loose over time.
- Allow movement - Unlike welding, rivets can flex and shift slightly under loading without cracking. This makes rivets ideal for materials subject to expansion/contraction or vibration.
- Quick installation - Automated riveting systems allow for fast mass production. Even manual riveting with simple hand tools is relatively quick compared to other mechanical fasteners.
- Reliable inspection - It's easy to visually confirm a properly set rivet. Bad rivets also tend to loosen quickly if improperly set.
- Cost-effective - Mechanical fasteners like rivets are economical, especially for medium to high production runs. The tools are reusable and don't require consumable materials.
Choosing the right rivet type and size is critical for strength and appearance. Considerations include:
- Materials - Rivet material should match or be compatible with the sheet metal material. This prevents galvanic corrosion.
- Sheet thickness - Longer rivets are needed to span thicker stacks of sheet material. A rivet should be 1.5-2x the combined thickness of sheets.
- Grip length - This is the length of unswaged shank needed to fit in the hole and expand. Allow at least 2x sheet thickness for grip.
- Hole size - Clearance between the rivet and hole impacts grip/expansion. The hole should be 1.1-1.5x the rivet diameter.
- Head shape - Countersunk, flat, or rounded heads are common. Match head shape to the desired visibility and feel.
- Strength - Larger and higher shear strength rivets increase joint strength. This is essential for dynamic loads.
Proper rivet selection will prevent failure while providing the desired appearance. Consulting manufacturers' technical guides is recommended.
While riveting may appear simple, proper techniques are needed for optimal results:
1. Hole Preparation - Holes must be round, clean, and sized appropriately for the rivets. Deburring is essential.
2. Parts Alignment - Sheets must be clamped or fixtured to ensure hole alignment through the stack.
3. Rivet Insertion - Rivets are inserted through the aligned holes with the head against one side.
4. Grip Setting - The jaws of a rivet gun squeeze the protruding shank to flare it slightly. This seats the rivet and establishes grip before swelling.
5. Hammering/Swaging - A hammering tool or squeezers compress the rivet shank to form the second head and fill out the hole. This expands the rivet for tight clamping.
6. Head Finishing - Any necessary finishing work is done to smooth and round the formed head.
7. Inspection - The set rivet should be visually inspected for proper head shape, full shank expansion, and tight clamping.
Proper techniques result in securely fastened, aesthetically pleasing rivets. Training and practice is key for developing riveting skill.
While riveting can be done manually, power tools increase speed and ease:
- Pneumatic rivet guns rapidly insert and flare rivets. They come in squeezer and hammer styles.
- Hydraulic squeezers use water pressure to compress rivets for uniform swelling. Allows one-handed operation.
- Computerized riveting machines combine insertion and swaging in a programmed sequence. Ideal for mass production.
- Bench and hand-held pneumatic hammers provide striking force for hand swelling. Require anvil support behind the workpiece.
- Anvils/bucking bars support the rivet tail during hammering. Various tip shapes aid in finishing rivet heads.
- Hole punch/drilling tools create consistently sized holes for rivets. Boosts quality and speed.
The right equipment allows efficient, high-quality rivet setting suited to production needs. Proper maintenance and safety procedures must be followed.
Applications of Riveting
Rivets have broad usefulness for permanently joining sheet metal:
- Aircraft and aerospace - Rivets are the preferred fastener for airplane assembly due to vibration resistance.
- Machinery - Rivets withstand shock loads better than screws or bolts on heavy equipment.
- Automotive - Cars use rivets for body panels, frames, and interior components.
- Appliances - Manufacturers use rivets on washers, dryers, refrigerators, and other products.
- Electronics - Rivets assemble external cases as well as internal components and circuit boards.
- HVAC ducts - Special blind rivets seal sheet metal ductwork sections.
- Building facades - Rivets attach various architectural metal elements while allowing movement.
- Furniture - Modest vibration resistance suits rivets well for furniture assembly.
Rivets meet the demand for sturdy yet flexible sheet metal fastening across industries. Advancements in automated riveting continue to spread its advantages.
The versatility, strength, and speed of riveting make it ideal for permanently joining sheet metal components. With attention to proper rivet sizing and installation techniques, manufacturers can produce top-quality fabricated products efficiently. Rivets will continue enabling innovative metal designs across diverse markets into the future. CNC Milling CNC Machining