Riveting in Sheet Metal(rivet types Jill)
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Types of Rivets for Sheet Metal
There are several types of rivets suitable for joining thin sheets of metal:
Solid rivets - These are one-piece rivets made entirely of steel. They are available with flat, round, or countersunk heads. Solid rivets require access to both sides of a joint for installation.
Blind rivets - These have a hollow body and mandrel through the center. Blind rivets are inserted from one side and are "set" when the mandrel is pulled creating an expanded bulb on the blind side. They don't require access to both sides of the workpiece. Common types are pop rivets and breakstem rivets.
Self-plugging rivets - These feature a wide, flare-shaped head that seals on the setting side. The rivet fills the clearance hole and keys cold metal into the wall of the hole for a tight fit. They are commonly used in high-strength lap joints.
Drive rivets - They have an unflared tubular body and are driven using pneumatic, hydraulic or hammer tools to flare out the tubular body. Drive rivets exert compression and create very stiff joints.
Tubular rivets - They have a hollow, cylindrical body and are flared at one end. Tubular rivets are typically used with soft materials like fabrics rather than sheet metal.
Rivet Joint Design for Sheet Metal
Proper rivet joint design is important to create a connection that has the required strength. Here are some key factors to consider:
- Rivet diameter - Larger diameter rivets are stronger than smaller ones. The rivet diameter should be matched to the sheet thickness.
- Spacing between rivets - Rivets must be spaced appropriately to distribute load across the joint. General spacing is 2-3 diameters between rivets in the direction of load.
- Edge distance - Rivets should be placed at least 1.5 times the rivet diameter from a sheet edge. This prevents the edge from curling or deforming under load.
- Lap distance - For lap joints, the overlap between sheets should usually be 1.5 to 3 times the rivet diameter to provide sufficient shear strength.
- Number of rows - Multiple parallel rows of rivets help distribute stress over a wider area for stronger connections.
- Materials - Rivet material should match or be stronger than the sheet material. This ensures the rivet fails after the sheet in an overstressed joint.
Tools for Riveting Sheet Metal
Installing rivets in sheet metal requires a riveting hammer or rivet gun to flare out the rivet body and form the head. Here are the main tool types:
- Manual riveting hammer - A hammer with a bell-shaped head for flaring rivets. The user hits the rivet to flare it.
- Pneumatic rivet hammer - Uses compressed air to drive a piston that flares the rivet when the trigger is pulled. Easy to use one-handed.
- Hydraulic riveters - Powerful hydraulic force flares the rivet quickly. Used for large or high strength rivets.
- Hand riveters - Have handles like pliers to squeeze and flare rivets. Good for occasional small rivet work.
- Pop rivet guns - Flare blind pop rivets when the handles are squeezed. Simple and fast for small pop rivets.
Rivet hammers require some skill to evenly buck the rivet and form a neat head. Rivet guns are quicker and easier but more expensive.
Riveting Process
Riveting sheet metal is generally a simple process that involves three main steps:
1. Drilling - A hole is drilled through the sheets at the desired rivet location. The diameter matches the rivet size. Holes should be perpendicular to the surface.
2. Inserting the rivet - The rivet shaft is inserted through the aligned holes in both pieces of sheet metal. The rivet head sits flush on one side.
3. Flaring the rivet - The hammering or squeezing action of the riveting tool flattens and spreads the rivet body to form a second head and clamp the sheets together.
For blind rivets, the mandrel is snapped off after flaring leaving a formed rivet head on the blind side. Rivets exert a strong clamping force on the joint.
Proper hole size, rivet length, and consistent flaring are key to getting a tight, strong connection. Setting all rivets to the same degree prevents distortion. Perpendicular driving helps maintain flush rivet heads.
Inspection and Testing
Once installed, riveted joints should be inspected to verify proper installation and strength. Checks include:
- Visual inspection of rivet heads - Confirm they are consistent and flush with no gaps between head and sheet.
- Confirm no cracks or fractures - Look for cracking of the rivet head or shank. Discard and replace any damaged rivets.
- Check for flexibility - The sheets should not move independently. Some minor flexing is normal.
- Shear testing - Sample riveted joints can be shear tested by applying transverse force to measure the connection strength.
- Tensile testing - Pull-off tensile tests determine if the rivets adequately clamp the material.
- Microscope inspection - The set rivet can be sectioned and inspected under a microscope to check for defects.
Proper rivet selection, joint design, installation, and inspection results in durable, permanent connections between sheet metal components that have the strength and longevity needed for the application. Riveting remains a highly useful joining process across many metal fabrication industries. CNC Milling CNC Machining