Rivets have been used for thousands of years but still play an important role in modern manufacturing, especially in computer numerical control (CNC) machining applications. This article will provide an overview of different types of rivets and their common uses in CNC.
One of the most popular types of rivets for CNC applications are blind rivets, also known as pop rivets. Blind rivets consist of a flanged hollow shaft and a mandrel through the center. Blind rivets are so named because they can be installed without access to the backside of the material.
To install a blind rivet, a specially designed rivet gun is used. The gun pulls on the mandrel which causes the rivet body to flare out and create a second head on the backside material. The mandrel snaps off flush after installation. Blind rivets come in various head styles and materials including aluminum, steel, stainless steel, and monel.
Common uses for blind rivets in CNC include:
- Joining sheet metal enclosures and covers
- Attaching components and brackets to panels
- Assembling electronic chassis and small assemblies
- Repairing panels and housings
The ability to install blind rivets from one side makes them ideal for automated CNC riveting applications. Installation is fast and efficient. Blind rivets also accommodate various material thicknesses.
Solid rivets consist of a single solid shaft without a mandrel. The rivet shaft is inserted into pre-drilled holes and a rivet gun or other tool is used to flare out the tail end of the rivet. This creates a formed head on the backside material that holds everything together.
Solid rivets are commonly used in CNC applications that require riveting of thicker, stronger materials. Some examples include:
- Joining steel plates, brackets, and frames
- Assembling heavy machinery housings and bases
- Riveting truck frames and agriculture equipment
- Permanently fastening parts that receive high stress and vibration
The lack of a hollow mandrel makes solid rivets stronger than blind rivets. Automated CNC machines can efficiently upset solid rivet tails to custom lengths for solid rivet installation.
Drive rivets consist of a smooth solid shaft without a head. They are primarily designed for use in automated riveting machines. Drive rivets are fed into a CNC-controlled pneumatic hammer that holds the rivet in place while a hydraulically driven plunger upsets the tail to form the head.
Drive rivets allow for very efficient automated riveting. The CNC machine can be programmed to insert and upset drive rivets into pre-drilled holes at high speeds. Typical applications include:
- Mass production riveting of appliances and electronics
- Riveting sheet metal parts like computer chassis
- Automotive drive train and powertrain riveting
- Permanent fastening of any components suitable for automated riveting
The smooth shafts of drive rivets permit fast feeding from vibratory bowl feeds into the CNC tooling. No mandrel removal is required as with blind rivets. Hundreds to thousands of drive rivets can be upset per hour with precision head shapes and lengths.
Tubular rivets, also known as closed-end tubular rivets, are sometimes used in CNC machining. They consist of a rolled tubular body that is open on one end and closed on the other end. The walls of tubular rivets are thinner than solid rivets.
The installation process involves inserting the open end into a pre-drilled hole. An automated rivet setting machine or manual hammer upsets and expands the closed end to flare out and form a head.
Tubular rivets have some advantages over solid rivets, including:
- Smoother finished appearance with no exposed rivet end
- Lower force and energy required for installation
- Tighter fit as the tubular shaft expands into the hole
Potential uses for tubular rivets in CNC applications include decorative fastening of panels, joining thin sheets, and fastening plastic components. However, their lower strength limits their use in high-stress CNC joints.
Rivet nuts provide threaded fastener capability combined with riveting installation. A rivet nut consists of a flanged threaded barrel portion and a thick mandrel. To install a rivet nut, the mandrel end is inserted into a pre-drilled hole. A rivet gun, squeeze yoke tool, or other method is used to deform the barrel, flare it outward, and secure the nut. The mandrel snaps off after installation.
Rivet nuts are beneficial for CNC applications where you need to attach panels or parts with bolts rather than rivets. The nuts become permanently locked into position when installed. Common uses include:
- Installing mounting plates and brackets
- Attaching access panels and doors
- Providing threaded attachment points for legs and feet
- Allowing adjustable positioning of components
In automated production, CNC machines can efficiently pick, place, and install rivet nuts into sheet metal and other materials. This permits threaded fastening and serviceability using standard bolts.
Self-piercing rivets (SPRs) combine piercing with flaring in a single-step installation process. SPRs feature a semi-tubular body with a rounded tip. Installation tooling forces the rivet through materials to interlock them. The tail end then flares outward to form a head and lock the rivet in place.
Benefits of SPRs for CNC applications include:
- No pre-drilling required prior to fastening
- Joint formation and fastening in one process
- Works on overlapping as well as butt-joined materials
- Installation into hard materials like steel and aluminum
Typical CNC uses include fastening of:
- Aluminum and steel sheets in enclosures and cabinets
- Mixed material assemblies like plastic to metal
- Multi-layered sandwich type panels
- Lap joints and hemming
The piercing action of SPRs allows automated CNC riveting of materials without separate drilling. Riveting and clinching combine into one seamless process.
Rivets continue to offer benefits in CNC machining and manufacturing applications. Various rivet types allow cost-effective joining of different materials with speed and efficiency. CNC automated riveting improves quality and throughput in high-volume production. Correct selection of rivet style and material ensures riveted joints have the required strength, appearance, and longevity. Whether using blind, solid, drive, tubular, nut, or self-piercing rivets, this traditional fastener still provides an effective way to assemble components with automated precision. CNC Milling