Riveting in Sheet Metal Fabrication(medical cnc machining Sherry)

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Rivets are a common and effective way to join together pieces of sheet metal. They create a strong mechanical fastening that holds up well even under stress. Understanding when and how to use rivets for sheet metal projects can help you create durable products.
What is a Rivet?
A rivet is a mechanical fastener that consists of two main parts - the rivet body and mandrel. The rivet body is a cylindrical shaft with a head on one end. The mandrel is inserted into the hollow end of the rivet body and helps hold the rivet in place during installation.
Rivets work by placing the rivet body into a pre-drilled hole in the sheets being joined. The empty end of the rivet is then flattened or 'bucked' against the material using a riveting hammer or compressed air rivet gun. This causes the rivet body to deform, creating a second 'shop head' that holds the rivet in place. The mandrel is also deformed in the process and locks the two rivet heads securely together.
Benefits of Riveting Sheet Metal
Using rivets to join sheet metal has several advantages:
- Strong and Durable Fastening - The interlocking rivet heads create a tight mechanical connection that is resistant to vibration and shock loads. Properly installed rivets can last for decades.
- Easy to Install - Riveting is a straightforward process that can often be done with simple hand tools. Installation only requires access to one side of a joint.
- Maintains Material Strength - Unlike welding, riveting does not significantly alter the heat treatment of the base metals. The joint maintains nearly the full strength of the original sheets.
- Adjustable Grip - The grip range of a rivet (the thickness it can clamp) can be specified by picking different rivet lengths. This allows flexibility for varied material thicknesses.
- Low Profile Heads - Rivet heads can be countersunk to create a flush surface if desired. This gives a smooth, finished appearance.
- Easy to Inspect - It is quick to visually inspect for proper rivet installation and look for signs of damage or loosening over time.
- Resists Vibration Loosening - The mechanical interference fit of rivets helps prevent loosening from vibration better than most other fasteners. Locking features can further improve resistance.
- Corrosion Resistant Options - Rivets are available in corrosion resistant materials including stainless steel and aluminum for use in harsh environments.
Using Rivets with Sheet Metal
For best results when riveting sheet metal, follow these guidelines:
Hole Size and Spacing
- Drill holes slightly larger than the rivet shank diameter to allow easy insertion. Generally 0.1 mm extra clearance is recommended.
- Space rivets no less than 2 times the sheet thickness apart to prevent distortion. More spacing may be needed for thicker/stiffer materials.
Joint Design
- Use at least 2 rivets per joint for alignment and load distribution. More may be required depending on the application.
- Locate rivets evenly spaced and symmetrically across from each other when possible.
- Place rivets perpendicular to the applied load for maximum strength.
- Allow at least 2x the rivet diameter of material edge distance to prevent tearing out.
Rivet Selection
- Softer rivet materials like aluminum deform more readily for better filling of the drilled hole. Use these for softer base materials.
- Harder materials like steel allow higher shear and tensile strength. Use these for harder/stronger base metals.
- For structural joints, look for rivets that meet military or aerospace standards for quality assurance.
Installation Process
- Use a rivet setter on the bucking end and hammer/squeeze riveter on the shop head end for best results.
- Buck the rivets evenly using moderate force. Over bucking can damage the surrounding material.
- Inspect the shop head for uniform shaping without cracks. The mandrel should break flush.
- Consider using self-plugging rivets. The mandrel stem shears off internally for a fully filled hole.
Maintenance and Repair
- Check for loose or damaged rivets periodically, especially after high load events.
- Drill out old rivets and reinstall new oversize replacements as needed for repairs.
- Touch up paint shop heads to protect against corrosion if operating in harsh environments.
Proper riveting technique helps create solid sheet metal assemblies and prevent failures. Consulting an experienced metal fabricator can provide further guidance on the best riveting practices for your specific application. With some care taken during design and installation, riveted joints will provide reliable performance even under demanding conditions. CNC Milling CNC Machining