Riveting in Sheet Metal Fabrication(weld lines injection molding Sandy)
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In this article we will look at what rivets are, the different types of rivets, and how riveting is used in sheet metal fabrication. We will also discuss best practices for riveting and some of the equipment involved like rivet guns.
What is a Rivet?
A rivet is a mechanical fastener that consists of two main parts - the rivet body and mandrel. The body is a head on one end, and a shank on the other. The shank is inserted through holes in the materials being joined, and the excess shank is upset using a riveting hammer or squeezed together using a rivet gun. This causes the rivet to expand and grip the materials tightly together.
The mandrel is a smaller shaft that runs through the hollow center of the rivet body. For many types of rivets, the mandrel is pulled out after the rivet has been set in place and expands. This creates a permanent solid fastening. Rivets come in a wide range of sizes, shapes and materials like aluminum, steel, titanium and more.
Types of Rivets
There are several types of rivets used in sheet metal fabrication. Some of the most common include:
- Solid/Semi-Tubular Rivets: As the name implies, these have a solid shank rather than a hollow tube. The mandrel is integrated into the rivet body. Hammering spreads the tail to set the rivet.
- Blind Rivets: These have no head on one end and can be set from one side of a joint. Pulling the mandrel expands the rivet body. Used where only one-sided access is possible.
- Pop Rivets: Have a pre-assembled stem that is pulled to expand the rivet. Quick and easy for DIY and low volume shop use.
- Drive Rivets: Also called squeeze rivets. These are set using powerful hydraulic tools to upset the rivet shank. Often used in automated production.
- Structural Rivets: Used for high-strength critical joints like in aircraft. Require specialized setters to prepare a very robust joint.
- Self-Plugging Rivets: Designed to seal the hole after installation. Useful for leak-proof joints.
- Specialty Rivets: There are many other variations like large flange rivets, tri-fold rivets, quick-lock rivets and more.
Rivet Materials
Rivets come in a range of materials suited to different applications. Common materials include:
- Aluminum - Lightweight, corrosion resistant, softest option. Used for sheet metal and other soft material fastening.
- Steel - Strong but prone to corroding. Often zinc plated or stainless steel. Used where high strength is needed.
- Copper - Corrosion resistant like aluminum but stronger. Often used in marine applications.
- Monel - Corrosion resistant nickel alloy stronger than copper. Used in demanding applications.
- Titanium - Very strong but expensive. Used in critical aerospace joints.
Using Rivets in Sheet Metal Fabrication
Riveting is a simple, reliable process used in countless sheet metal products. Here are some benefits of riveting:
- Quick to assemble - no threading, tapping or curing required. Just drill holes and set rivets.
- Only access to one side needed for blind rivets.
- Loose parts fastened securely. Vibration resistant.
- Adjustments can be made by drilling out rivets.
- Variety of materials and strengths available.
- Simple equipment - just a rivet gun or hammer required in most cases.
- Relatively low skill needed for basic riveting work.
Disadvantages include limited disassembly ability and lower strength compared to bolts. Usage must be in alignment with rivet strength, sheet thickness and demands of the application.
Riveting Process
The riveting process generally involves:
1. Drilling or punching holes - Holes are created in each piece to be joined at the locations where rivets will be set. Hole diameter depends on rivet size. Bolts can often be replaced with rivets of the same diameter.
2. Hole alignment - Materials to be riveted must be clamped or fixtured so holes line up precisely. Misalignment will make setting rivets very difficult.
3. Rivet selection - Proper rivet length and material must be selected. Too short won't grip enough material and too long will bottom out.
4. Insertion - Rivets are inserted through the aligned holes. Blind rivets are inserted head first. Solid rivets are oriented head outwards.
5. Setting - Rivets are compressed using the appropriate tooling to flare out and adhere to the sheet metal. This permanently joins the materials together.
6. Inspection - Rivets should be checked for proper setting. Loose rivets must be replaced.
For critical applications, solid rivets are often heat treated after installation to relieve stress and increase strength.
Riveting Equipment
Setting rivets is done using rivet guns, rivet hammers or squeezers. Here are some of the main types of equipment:
- Pneumatic Rivet Guns - Air powered for rapid, repeated rivet setting. Different size and power levels. Light duty for pop rivets, heavy duty for large solid rivets.
- Hydraulic Riveters - Use hydraulic pressure to pull mandrels and upset rivets. Available in portable hand tools up to 20+ ton shop presses. Allow high force with smooth action.
- Battery Rivet Guns - Cordless electric tools for portable convenience without a compressor. Limited rivet size and lower power than pneumatic.
- Air Hammers - Pneumatic hammers with rivet set attachments are an economical option for solid rivet setting. Versatile but require operator skill.
- Hand Squeezers - Pliers-like tools for manually setting blind rivets. Lower strength limits their size.
- Rivet Spinners - Used to flare solid rivet tails quickly by hand after hammering. Improves appearance and security.
- Hole Punches - Cut holes instead of drilling for quick preparation. Limited to thin sheets and small holes.
- Backing Plates - Steel blocks placed behind the rivet site support against deformation while setting.
Proper tool selection helps ensure quality rivet joints. Heavy duty tools have more hitting power and won't stall on tough jobs.
Best Practices for Riveting
Some tips for achieving good results riveting sheet metal include:
- Use roughened or dimpled sheet metal surfaces to increase grip. This stops slippage.
- Rivets should fit holes snugly before setting. Oversize holes won't allow proper deformation.
- Apply pressure on the joint when setting rivets. Backing plates or clamps help.
- Set rivets starting from the center and move outwards. This avoids distortion.
- For solid rivets, set the head first with multiple hits to flair. Then set the tail.
- Inspect set rivets for: centered bump, full circumference flare, no cracks or loosening.
- Consider heat treating or aging after riveting high strength alloys to prevent failure.
Proper drilling, hole alignment, rivet selection and setting technique results in secure, lasting riveted joints.
Conclusion
Riveting is an essential process in working with sheet metal. It allows fastening together panels and parts with accuracy and strength. While other methods like welding and bolting have their place, riveting remains a key assembly method thanks to its simplicity, reliability and economy.
Understanding the various types of rivets along with proper equipment and installation techniques allows creating high quality riveted products. Riveting skills come quickly with practice, and allow the fabrication of aircraft, vehicles, ductwork, enclosures, furniture and countless other sheet metal items using this fundamental mechanical fastening method. CNC Milling CNC Machining