High Quality Rivets for Precision CNC Machining(metal parts Oswald)

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Rivets are a crucial component in many manufacturing and engineering applications, allowing rigid fastening between plates, sheets and components. For projects involving computer numerical control (CNC) machining, having high quality rivets is essential for achieving precise, reliable and robust end results. In this article, we'll explore key considerations for choosing top-grade rivets suited for CNC machining and manufacturing.
Material Properties
The material used for rivets greatly impacts their performance and suitability for CNC applications. Common materials include various steel alloys, aluminum, titanium, brass and copper. Key factors to evaluate are:
- Strength - The rivet must withstand shear and tensile stresses involved in the fastening application. High strength materials like carbon steel and certain stainless steel alloys are frequently used.
- Machinability - Materials that are readily drillable, tapable and profileable using CNC tools are preferred. Softer materials like aluminum and brass offer superior machinability compared to very hard alloys.
- Corrosion Resistance - Material choice depends on the operating environment. Stainless steels offer excellent corrosion resistance if high water or moisture exposure is expected.
- Weight - Lower density materials like aluminum or titanium alloys allow lightweight rivet design. This is crucial in applications like aerospace.
- Conductivity - Copper and aluminum provide high thermal and electrical conductivity, an important factor for some assemblies.
- Cost - Common, inexpensive metals like carbon steel or aluminum are suitable for most non-specialized applications. Exotic alloys add cost.
Hardness and Strength Specifications
The hardness and tensile strength of the rivet metal is critical. Rivets must accommodate shearing and compressive stresses during installation and the clamping forces keeping the assembly together. Hardness is commonly specified using scales like Vickers, Rockwell or Brinell. Grade identification systems (e.g. ASTM specifications) also indicate strength levels.
The desired hardness and strength depends on the materials being joined and the forces involved. Using rivets with appropriate physical properties prevents failure or deformation when tightened and loaded. It also allows properly controlled deformation to flare the rivet tail and lock it in place.
Precision Manufacturing
For CNC machined components and assemblies, rivets must offer dimensional precision and consistency. Factors to evaluate include:
- Diameter tolerance - The shank diameter must tightly match the rivet holes. Diameters are normally controlled to tolerances of +/- 0.002” or tighter.
- Roundness - Precision rivets have round shank cross-sections free of ovality. This prevents binding during installation.
- Straightness - Any deviation from straightness makes insertion difficult. Rivet straightness of 0.010” TIR or better may be mandated.
- Head and tail concentricity - Off-center heads or tails alter the installation forces and can complicate CNC fabrication. True position tolerances as tight as 0.002” are used.
- Surface finish - Smooth, burr-free finishes prevent galling, buckling, and friction during insertion and driving. Max RMS values from 8 to 32 are typical.
These parameters are normally guaranteed through careful material sourcing, forging, machining, and quality control by the rivet manufacturer. Using precision rivets enhances efficiency and reliability in CNC projects requiring tight tolerances.
Rivet Head Styles
Several head configurations are available for blind and through-hole rivet applications:
- Countersunk - Flat, tapered heads fit flush into counterbored holes for an even surface. Common in aerospace.
- Universal/Flat - Cylindrical low profile heads. Used for general applications.
- Large Flange - Wide, flat heads to distribute load over more material.
- Brazier - High domed head for excellent grip and leverage during installation.
- Modified Brazier - Reduced dome height to minimize protrusion.
- Large and Small Hex Head - Hex shaped head with wrench flats for driving and removal.
The chosen head shape depends on the fastening method (manual or pneumatic), hole type, grip range, and assembly constraints. CNC programming should account for specific head dimensions and geometries that affect tool paths and final fit.
Rivet Insertion and Driving
During CNC control programming, proper insertion and driving techniques must be considered. Pneumatic or manual processes deform the tail to flare it and lock the rivet in place. Key parameters include:
- Identical hardness for rivet and workpieces - Prevents cracking from deformation.
- Hole diameter and pretapping - Must allow rivet insertion but grip tightly.
- Insertion speed - Affects frictional heat and galling. Approximately 100-200 inches/minute.
- Drive force, stroke distance, and impact energy - Must thoroughly flare the tail without damaging the material or assembly.
- Tool type and tip geometry - Determines application force distribution.
- Number of strikes - More impacts increase flaring but risks part damage.
- Process monitoring - Force, displacement, or acoustic sensors confirm proper setting.
By integrating these factors into CNC code, optimal rivet setting can be achieved. This maximizes joint strength and minimizes rework.
Rivet Quality Control
All critical rivet properties and characteristics should be verified through adequate quality control and assurance practices:
- Dimensional inspection - Sample testing using precision gauges, micrometers, and optical comparators.
- Hardness testing - Rockwell and Brinell hardness tests confirm strength levels.
- Tensile testing - Confirms minimum tensile strength and ductility by destructive testing.
- Chemical analysis - For alloys, verifying the composition ensures correct properties.
- Microscopy - Shows surface defects and internal discontinuities.
Reputable rivet manufacturers provide certificates of conformance backed by rigorous quality control at all stages. Using certified rivets enhances CNC machining success.
In summary, choosing high quality rivets is key for precision CNC machined products. Careful material selection along with proper hardness, dimensional precision, head styles, insertion methods, and quality control allows rivet joints to meet demanding functional requirements. With an optimized riveting process integrated into CNC code, manufacturers can achieve reliable and consistent builds. CNC Milling CNC Machining