CR3243-4-8 - Cherry Aerospace CherryMax Rivet

CR3243-4-8 – Cherry Aerospace CherryMax® 100° Flush Head Rivet

Available now on the Airparts.aero Marketplace.

Overview

The Cherry Aerospace CR3243-4-8 is a premier, high-strength, bulbed, mechanically-locked blind rivet, representing the pinnacle of aerospace fastening technology. This is not a simple "pop" rivet; it is a flight-critical structural fastener engineered for applications where access to the blind side of the structure is impossible. The "CherryMax®" system is renowned for its reliability, consistency, and superior vibration resistance. The CR3243-4-8 is specifically designed with a 100° countersunk flush head for aerodynamically critical surfaces. Its unique design features a mechanically locking stem that is virtually immune to the effects of vibration, preventing stem loss which is a common failure mode in lesser blind fasteners.

The installation of a CherryMax® rivet forms a large, load-bearing bulb on the blind side, providing a greater footprint than standard plug-type rivets. This distributes the load over a wider area, making it ideal for use in thin-sheet applications and composite structures. The flush-breaking stem, combined with the positive mechanical lock, ensures a high-quality, inspectable, and time-efficient installation, making it a preferred fastener for both OEM production lines and A&P mechanics performing structural repairs in the field.

Key Features

• Mechanically Locked Stem: A separate locking collar is swaged into the rivet head, creating a positive mechanical lock for the stem, ensuring maximum vibration resistance and eliminating the risk of stem loss.

• Bulbed Blind-Side Footprint: Forms a large, expanded bulb on the blind side, providing a broad bearing surface for high shear and tensile strength.

• Wide Grip Range: A single rivet part number can accommodate a wide range of material stack-up thicknesses, simplifying inventory and preventing installation errors.

  
  

  
  

• 100° Flush Head: The countersunk head design allows for a smooth, flush finish on external aircraft skins, minimizing aerodynamic drag.

• Flush-Breaking Stem: The stem is designed to break flush with the rivet head, minimizing or eliminating the need for post-installation shaving.

• Multi-Material Construction: Utilizes an optimized combination of materials (aluminum sleeve, alloy steel stem, Monel collar) for superior performance.

Technical Specifications

• Part Number: CR3243-4-8

• Component Type: Mechanically Locked, Bulbed Blind Rivet

  
  

  
  

• OEM Manufacturer: Cherry Aerospace (a division of PCC Fasteners/SPS Technologies)

  
  

  
  

• Head Style: 100° Countersunk Flush Head

• Shank Diameter: -4 (4/32" or 0.125 inches)

• Maximum Grip Length: -8 (8/16" or 0.500 inches)

• Grip Range: 0.438" to 0.500"

  
  

  
  

• Material (Sleeve): 5056 Aluminum Alloy

• Material (Stem): Alloy Steel

• Material (Locking Collar): Monel

• Finish: Color-coded (Blue) for grip identification.

• Governing Specifications: Exceeds the requirements of NAS 1399. Conforms to Procurement Specification NASM9035.

Aircraft Compatibility

• Universal Application: CherryMax® rivets are a structural standard used across the entire aerospace industry. They are specified for production and repair on virtually all modern aircraft, including those manufactured by:

  • Boeing, Airbus, Textron Aviation (Cessna, Beechcraft), Lockheed Martin, Bombardier, Embraer, Piper, and more.

Note: The specific application of the CR3243-4-8 must be verified against the aircraft's Structural Repair Manual (SRM) or engineering drawings. The choice of rivet material, diameter, and grip length is a critical engineering decision.

Applications

• Structural Airframe Assembly: Attaching skin panels to stringers, ribs, and frames where blind-side access is limited.

• Field Repair: The primary fastener for performing certified structural repairs in accordance with an SRM.

• Composite Structures: The large blind-side footprint makes it ideal for fastening composite materials without delamination.

• High-Vibration Areas: Used in areas subject to significant vibration where the mechanical lock is essential, such as nacelles, pylons, and areas near control surfaces.

Why Choose CR3243-4-8?

The CherryMax® CR3243-4-8 is an engineered system, not just a fastener. Its key advantage is the mechanically locked stem, which provides a level of structural integrity and vibration resistance that friction-locked or plug-type rivets cannot match. In a critical structural application, a lost stem compromises the joint's shear strength and creates a path for moisture intrusion. The CherryMax® design provides a visually inspectable, positive-locking solution that saves installation time and guarantees long-term performance. For any structural application requiring a blind rivet, the CherryMax® is the industry standard for safety and reliability.

The engineering principle that distinguishes the CherryMax® rivet is its positive mechanical lock, achieved through a process of controlled plastic deformation. During installation, the pulling head of the installation tool applies a tensile force to the stem. This force first forms the blind-side bulb. As the pulling pressure continues to increase, it overcomes the compressive strength of the separate Monel locking collar. The tool's jaws then actively swage this collar into a conical recess in the rivet sleeve's head and simultaneously into a corresponding locking groove on the stem. This action creates a permanent, 360-degree interference fit, mechanically locking the stem into the sleeve. The stem is designed with a break-notch that will only fracture once this locking action is complete, providing a built-in quality control check. The result is a monolithic, multi-material fastener with quantifiable shear and tensile strengths and a locked stem that cannot dislodge under vibration.

Note: The CR3243-4-8 is a flight-critical fastener. It must be installed using the correct, calibrated Cherry Aerospace tooling, including the specified pulling head (e.g., H701B-456) and riveter. Using improper or uncalibrated tooling will result in an incorrect installation, compromising the structural integrity of the joint. Installation must be performed by a certified mechanic in accordance with the Structural Repair Manual (SRM) or other approved data.

Documentation

• Cherry Aerospace® Website: While direct links to individual part number spec sheets are not common, comprehensive technical data, standards, and installation guides for the CherryMax® family of fasteners can be found on the official PCC Cherry Aerospace® website.

  
  

  
  

• NASM9035: The procurement standard that governs the manufacturing and quality of this rivet.