High Quality Rivets for Precision CNC Manufacturing(insert molding design guide Fanny)
- source:YESCOM CNC Machining
For companies utilizing computer numerical control (CNC) machining, selecting the optimal rivets is critical for precision assembly and enduring product performance. This article will examine the properties and applications of different rivet types commonly used with CNC manufactured components.
Blind rivets, also known as pop rivets, are among the most popular rivet choices for CNC fabrication. As the name implies, blind rivets can be inserted and fastened from one side of a material without requiring access to both surfaces.
The blind rivet design features a rivet body and mandrel. To set the rivet, the rivet body is placed in a pre-drilled hole in the materials being joined. The mandrel stem is then pulled via rivet gun, clamping the materials together. The stem breaks off at a notch point, leaving just the rivet body securely set in the hole.
Blind rivets are available in a wide range of materials, finishes and diameters. Popular options include steel, aluminum, stainless steel and monel. Finishes can be plain, colored or weather resistant. Diameters generally range from 1/16 inch to 1/4 inch.
The one-sided installation of blind rivets makes them ideal for CNC fabrication of panels, sheets, frames and other assemblies where access is limited to one side. They provide a clean finish with no hardware protruding from the opposite side. Strength can rival bolts in certain applications.
Self-piercing rivets (SPRs) offer another blind riveting option gaining popularity in CNC manufacturing. As hinted by their name, SPRs do not require pre-drilled holes. Instead, a semi-tubular rivet pierces through stacked sheets of material when the rivet gun is fired.
As the rivet partially punches through the top layer, a specially angled tip flares out the bottom layer, joining the sheets between the flattened rivet head and tip. The result is a solid clinching of materials without the need for drilling. It also avoids the hollow cavity formed beneath traditional blind rivets.
Self-piercing rivets are ideal for automated high-volume production on CNC machines. Their ability to pierce and fasten in one step improves cycle times over drilling and riveting as separate operations. The clinching also creates a tighter joint with greater leak resistance compared to standard blind rivets.
Materials commonly joined with SPRs include steel, aluminum and composites. Cover sheets usually range from .8mm to 2.5mm thick, with maximum stack heights around 4mm to 8mm. Rivet strength is roughly equivalent to a standard rivet, though dependent on materials clinched.
When strength is the utmost priority, structural rivets deliver unmatched performance. Made from solid aluminum or steel alloys, these rivets exhibit very high shear and tensile strength. Their large head diameter and tight clinch also provide excellent vibration resistance.
While standard rivets work well for static applications, structural rivets are often mandated by building codes and engineering specifications for structural fabrication and construction. CNC machined components under dynamic loads likewise benefit from the enhanced strength of structural rivets.
The riveting process for structural rivets involves drilling or punching an appropriately sized hole, inserting the rivet and bucking off the tail end to form a clamping head. This creates a tightly clenched joint that resists forces from multiple directions. Proper hardware and operator training is critical to achieve full rivet strength.
Options like flat head and countersunk head structural rivets allow for rivet installation that is flush with the surface material. Though more expensive than common rivets, the extreme durability of structural rivets makes them well worth the investment for critical CNC machined parts and assemblies.
For the highest strength in permanent fastening, shoulder lockbolts are an excellent choice. These two-piece fasteners consist of a bolt and collar that create joints stronger than standard nuts and bolts.
The bolts feature serrated shoulders below the head that mate with a corresponding serrated collar. When tightened together, the collar displaces outward and the serrations mesh for an extremely secure clinch. The joint withstands severe shear, tensile and vibratory forces.
Shoulder lockbolts are installed using standard drilled holes. A selection of head styles allows for flush final finishes. While the bolts can be removed and replaced a few times, their optimal strength comes from one-time permanent assembly. The clinched collar effectively resists any loosening.
These capabilities make shoulder lockbolts well suited for critical CNC machined applications like truck frames, railroad rolling stock, industrial equipment, motors, pumps and more. The ability to precisely control torque and angular position of the lockbolts on CNC machines enables optimal joint integrity.
In some cases, threaded fasteners may be preferred over rivets. Rivet nuts provide a creative solution, combining the speed of riveting with the utility of tapped threads.
These fasteners feature internal threads and large flanges exterior to the threads. Installation tools upset and flatten the flange, forming a wide clamping surface against the underside of the host material. This creates a threaded insert that functions like a nut.
Rivet nuts are quick and easy to install in CNC machined parts, requiring only a drilled or punched hole. The flange provides very strong resistance to rotation and pullout loads. Steel varieties can even replace welded nut plates in many instances.
Since rivet nuts create instant threads on demand, they eliminate the need to tap holes in CNC production. Fasteners like bolts and screws can be mated with rivet nuts during final assembly, allowing fast disassembly if needed. Rivet nuts help reduce hardware inventories by consolidating threaded inserts and separate nut hardware.
Selecting Quality Rivets
With so many types and specs for rivets and related hardware, selecting the right option for your CNC manufacturing application is critical. Here are key factors to consider:
- Strength – How much shear and tension load must the rivet withstand in service?
- Access – Is blind riveting needed or is two-sided installation possible?
- Disassembly – Permanent vs. temporary fastening needs.
- Materials – Material compatibility for corrosion resistance, galvanic isolation, etc.
- Fastening Stack Height – Total thickness of materials being joined.
- Cost – Higher strength rivets often have a higher cost.
- Automation – Ease of automated fastening on CNC machines.
Reputable rivet manufacturers have technical staff available to collaborate on selecting ideal rivets and hardware for your manufacturing processes and product performance requirements. Prototyping can help validate the optimal solutions before high-volume production.
Investing in high quality rivets and related installation equipment pays dividends through enhanced product lifetime, safety and reliability. For today's precision CNC manufacturing, yesterday's humble rivet continues playing an important role. CNC Milling CNC Machining