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How To Determine The length Of SPR Rivets For Auto Body Panels

Pro Line Systems International-Auto Body Shop Equipment
Published by Pro Line Systems in Informational · Saturday 19 Oct 2024
Tags: HowToDetermineThelengthOfSPRRivetsForAutoBodyPanels
Determining the Proper Length of Self-Piercing Rivets for Auto Body Repair

First And Formost:
Always seek the auto manufacturers recommendations for proper size and length of SPR's
for the specific model and structure you are replacing.

Let's Dive In
When it comes to auto body repair, using the right fasteners is crucial for ensuring a strong and durable connection between metal panels. Self-piercing rivets (SPRs) are a popular choice due to their ability to join various thicknesses of metal efficiently without drilling holes.

However, determining the proper length of these rivets can be a bit tricky. Here’s a guide to help you make the right choice a lot easier.

  • Understanding Self-Piercing Rivets
Self-piercing rivets are designed to penetrate and deform the materials being joined without the need for pre-drilled holes. They work well with different metal thicknesses, making them ideal for auto body repairs. However, the effectiveness of an SPR depends heavily on its length in relation to the materials being joined.

how to determine the proper length of SPR

Clamp the panels together and measure total stack, or thickness.

The general rule of thumb is total stack + 2 mm equals the length of the SPR. Only use this formula if factory packaged rivets are not available or for a quick check on the factory rivet.

In this example, we have a thickness of 4.92 mm + 2 mm = 6.92 mm. A 7 mm SPR is needed.

Next, glue is applied to both mating surfaces and spread out evenly. Another bead is applied (no spread out) for bond line thickness. Clamps are used to compress the sheets.

Measuring to determine the proper length of SPR

Measure the total thickness of the stack with the adhesive.

Continuing with this example, 5.98 + 2 mm = 7.98 mm. An 8 mm SPR is now needed.

Always measure the thickness of the stack as it would be used on the vehicle for test panels when rivet bonding and weld bonding.

Once a correct rivet length has been determined, the amount of pressure to set the rivet needs to be checked.

Know how to use and adjust your riveter for best results. Always check the car manufacturers website for detailed SPR riveting information.

Factors to Consider
  • Material Thickness:
The combined thickness of the materials is the primary factor in determining the rivet length. Generally, you’ll need to consider the thickness of both panels being joined.

  • Material Type:
Different metals (steel, aluminum, etc.) have varying properties that may influence the choice of rivet length. Harder materials may require longer rivets to ensure adequate penetration.

  • Rivet Design:
The design of the rivet, including its head style and shank diameter, can also affect its length requirements. Ensure that the chosen rivet type is compatible with the application.

  • Rule of Thumb for Rivet Length
A common rule of thumb for determining the appropriate length of a self-piercing rivet is:
Total Thickness of Panels + 1/8 inch (3.2 mm):
This guideline accounts for the rivet's need to penetrate both panels and allows for sufficient deformation to create a strong bond.

  • Example:
• If you are joining two panels where one is 1.0 mm thick and the other is 1.5 mm thick, the total thickness is 2.5 mm.
Applying the rule of thumb: 2.5 mm + 3.2 mm = 5.7 mm
In this case, you would select a rivet that is approximately 5.7 mm in length. Adjusting for Material Variability.

While the rule of thumb provides a solid starting point, it’s essential to adjust based on specific conditions:

  • Variations in Material Thickness: If the thickness varies significantly, use the thicker panel’s measurement for more accurate rivet length.
  • Hardness of the panels.
  • Surface Condition: Ensure that surfaces are clean and free of debris to allow proper rivet penetration. Rough surfaces may require longer rivets.
  • Environmental Conditions: For applications exposed to extreme conditions (like heat or corrosion), consider using rivets with coatings or finishes that enhance durability.

Testing and Validation
Once you've selected a rivet length based on the guidelines, it’s wise to perform a few test installations.

self piercing rivet installation example

Check for:
  • Proper penetration into both materials
  • Adequate deformation of the rivet
  • A solid, stable joint without any movement

SPR Test Panel

Looking at the test sample above, the pressure of 6 bars = 60 PSI is the best pressure setting in this case.
This practical validation will help ensure that your chosen rivet length meets the demands of your specific repair job.

Final Thoughts
Selecting the proper length of self-piercing rivets is critical for achieving strong and reliable joints in auto body repair. By following the rule of thumb and considering the specific factors related to your materials, you can ensure a successful repair that stands the test of time. Always remember to test your installation for the best results, and you’ll be well on your way to mastering the art of auto body repair with SPRs!

The following resources and industry professionals are available to dig deeper into this subject.

1. Society of Automotive Engineers (SAE):
SAE provides technical papers and standards related to automotive manufacturing and repair, including guidelines on fasteners and joining technologies.

2. American Welding Society (AWS):
AWS offers resources on various joining methods, including self-piercing rivets, and their best practices for different materials.

3. Rivet and Fastener Manufacturers:
Companies like Hilti, Arconic, and Böllhoff often publish technical datasheets and guidelines on selecting and using self-piercing rivets.

4. Industry Training Programs:
Look for training programs or certifications offered by organizations like I-CAR (Inter-Industry Conference on Auto Collision Repair), which cover modern joining techniques in auto body repair.

5. Automotive Repair Textbooks:
Books such as “Automotive Body Repair and Painting” by James E. Duffy often include sections on fastening methods and materials.

6. Expert Interviews:
Reaching out to professionals in the auto body repair field, such as certified collision repair technicians or educators at automotive trade schools, can provide valuable insights and first-hand experience.
By including references to these resources, your blog post will not only be informative but also backed by reputable industry knowledge.

FYI: Giulio Valle, the founder of Pro Line Systems International, is a great resource to get answers to any questions about Self Piercing Riveting. Give him a call at: 305-793-9503

Here are some other Blog posts by Giulio Valle that touches on many other aspects of Self-Piercing Riveting you should check out. Knowledge Is The Mother Of Success!

  • The Future Of Self Piercing Riveting For Auto Body Repair.

  • The Most Advanced SPR Riveting Workstation In The World

  • Tips For Using Self-Piercing Rivets For Auto Body Repair

  • Self Piercing Riveting In The Auto Body Shop Explained - What You Need To Know

*For more information about ordering, or if you just need more tech information
Contact: Giulio Valle, at Pro Line Systems International Inc. For A Great Deal!

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FYI: Hey, Curious about Giulio Valle, the Authoritative Author, and creator of this Blog and the
Pro Line Systems Website? Check Out Giulio's Interesting Brief Biography Here. What A Guy!
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