Riveting in Sheet Metal Fabrication(metal surface finishes Bennett)
- source:GAENOR CNC Machining
Rivets in sheet metal work have numerous advantages that make them a popular choice:
- They create a strong, permanent joint. The deformation of the rivet shank locks the rivet in place.
- Installation is quick and requires simple equipment. Blind rivets can be set with only hand tools.
- The joint maintains flexibility after riveting. Parts can still shift slightly relative to each other.
- Riveting distributes stresses over a larger area compared to other fasteners.
- No drilling or tapping is required. The rivet shank displaces the sheet metal when driven in.
- Riveted joints maintain integrity even if the rivet loosens slightly over time.
- Installation causes minimal damage to the materials being joined.
- Riveted assemblies can be disassembled for repair if necessary by drilling out the rivets.
For these reasons, riveting is commonly used in many sheet metal applications including HVAC ducts, electronic enclosures, aircraft skin, and automobile body panels. The basic riveting process involves four steps:
1. Drilling or punching holes for the rivets. Holes are matched between overlapping pieces so the rivet shank passes through both sheets.
2. Inserting the rivet into the hole. Solid rivets are inserted head first. Blind rivets are inserted head last.
3. Setting the rivet, which deforms the rivet shank to clamp the sheets together. This may be done by squeezing a tool handle for blind rivets. Solid rivets require access to both sides.
4. Forming the shop head. On solid rivets, the shop head is formed by hammering or pressing against the rivet shank end. Blind rivets have a preformed shop head that folds out during setting.
CNC machining has helped automate parts of the riveting process for mass production. CNC hole drilling provides rapid, precise, and repeatable rivet holes. CNC punching machines can make hundreds of holes per minute with minimal setup between jobs. Automatic riveting systems then install each rivet in seconds while maintaining consistent quality.
Here are some recommended practices for riveting sheet metal with CNC equipment:
- Choose a suitable rivet material and size. Softer rivets like aluminum deform more easily. Larger diameters grip more strongly.
- Design overlapping joints so the rivet passes through at least 2 times the thinnest sheet thickness. More overlap provides a stronger connection.
- Keep minimum spacing between rivets and sheet edges. Typically at least 3 times the rivet diameter.
- Use punched or drilled holes - avoid burned holes from laser/plasma cutting that may interfere with rivet setting.
- Make sure material surfaces are clean before riveting to prevent compromised joint strength.
- Use quality tools in good condition and replace rivet setters as needed to get a good set.
- Apply pressure directly in-line with the rivet axis when setting solid rivets.
- Set blind rivets firmly until the pin breaks off and the shop head folds fully outward.
- Make sure both sheets are clamped tightly together during riveting to avoid elongation of the hole.
- Stagger the location of rivets in a pattern to evenly distribute load across the joint.
- Conduct sample testing on scrap pieces to verify hole size, rivet grip range, and set strength.
With CNC capabilities, riveting sheet metal has never been faster or more consistent. Parts can be processed in a matter of minutes that previously took hours or days by hand. By following best practices and taking advantage of automation, manufacturers can utilize rivets to produce all kinds of durable and reliable sheet metal assemblies. The versatility and simplicity of rivets will ensure they remain a trusted fastening method for countless sheet metal applications. CNC Milling CNC Machining