Quality Rivets - The Key to Durable and Reliable CNC Machined Parts(delrin Upton)
- source:YESCOM CNC Machining
When sourcing rivets for your CNC machining needs, here are some key factors to consider to ensure you are using only top quality, high performing rivets:
Material Grade and Hardness
Rivets come in a range of materials, with steel, aluminum, and titanium alloys being some of the most common. The material grade and hardness rating determine the rivet's strength and suitability for different applications.
For heavy duty structural parts, high strength steel rivets with grades 4.8 or 5.6 are recommended. They offer superior shear and tensile strength. For parts exposed to high temperatures or corrosive environments, stainless steel or titanium rivets are the best options.
Aluminum rivets are lightweight and lower cost, but compromise on strength. Ensure the aluminum grade matches the required structural loads. 7075 aluminum rivets offer the best combination of light weight and strength.
The dimensional accuracy of the rivet shaft and head is critical, as undersized or oversized rivets can cause issues during automated riveting on CNC machines. Reputable rivet suppliers will provide dimensional tolerances and ensure rivets consistently fall within the stated size range.
Rivets with excess variation in shaft diameter or inconsistent head shapes can lead to loose rivet joints or jamming during automated fastening. Always inspect rivet samples and request dimensional certification before purchasing large batches.
Rivet Gripping and Shear Strength
A key indicator of rivet quality is the gripping strength between the rivet head and shaft. Quality rivets are specifically engineered to produce a tight, non-rotating grip when installed in a properly sized hole. This distributes stresses evenly and prevents premature rivet head shear.
The rivet shear strength should also match or exceed the required loads for the part being fastened. Reputable suppliers will provide shear test data to guarantee their rivets will perform reliably in the field.
Surface Finishes and Coatings
The surface condition of rivets directly impacts their performance. Rivets should have a smooth, uniform surface free of flakes, pits, cracks or other defects that can initiate failure points.
Certain coatings and platings can also enhance rivet performance. Zinc, cadmium, anodized aluminum, and passivated stainless steel coatings protect against corrosion and galling. Solid lubricants reduce friction during the riveting process. Specify these special finishes when required by the application.
Lot Traceability and Testing
For critical CNC machined components, it is important to have full traceability and quality control testing data for the rivet lot being used. Rivet lots should be packaged and identified by the supplier in a manner that enables tracing back to the specific production run and quality control checks.
Reputable suppliers will furnish rivet testing certificates verifying the lot meets stated specifications for dimensions, hardness, shear strength, corrosion protection and other key attributes. This provides assurance for high-reliability applications.
Rivet Design and Geometry
In addition to material and dimensional factors, the physical design of the rivet can impact performance. The head shape, shaft diameter ratios, chamfers, undercuts and other geometrical factors should be optimized for the specific CNC machining process and required fastening strength.
Consulting with experienced rivet design engineers can help identify the optimal rivet style for an application. Custom designed rivets are recommended for the most demanding or specialized needs.
Automated Riveting Process Control
To achieve consistent quality riveted joints, the automated CNC riveting process must be dialed in and continuously monitored. Feeder systems, insertion speed, join pressure, hole sizing and other process factors require calibration to match the specific rivet type and strength needs.
Real-time monitoring of rivet lower head formation after insertion is key to ensuring a tight joint. Statistical process control should be implemented to detect any deviations promptly.
By considering each of these factors when sourcing rivets for CNC machined parts and products, manufacturers can ensure they are using the highest quality, most reliable, and consistent rivets for their automated production needs. Taking the time to qualify rivet suppliers, inspect rivet quality, match rivets to part requirements, and finetune CNC riveting processes gives the end product its best chance of meeting design life expectations and avoiding premature field failures. The small investment in quality rivets is well worth it for achieving maximum part durability, performance, and safety. CNC Milling CNC Machining