HL75-6A – Textron Aviation OEM Hi-Lok Tension Collar
Available now on the Airparts.aero Marketplace.
Overview
The HL75-6A is a genuine OEM, flight-critical Hi-Lok tension collar, a key component of the high-strength, two-piece Hi-Lok fastening system. This collar is specifically engineered for use with a corresponding -6 (3/16") diameter Hi-Lok pin in structural applications where the joint is subjected to significant tensile (pulling) loads. Unlike a standard shear collar, the HL75-6A features a larger diameter and bearing surface to better distribute high clamp loads. Manufactured from high-strength aluminum alloy, it features a frangible hex that shears off at a predetermined torque, ensuring a precise and consistent preload is achieved on every installation.
Key Features
- Tension-Rated Design: Engineered with a larger bearing face and greater mass than a standard shear collar (e.g., HL86 series). This allows it to safely handle high tensile loads and transfer them effectively from the pin to the structure without deformation.
- Automatic Torque Control: The collar features an external hex portion designed to shear off when the correct installation preload is reached. This removes operator-to-operator variability and guarantees that every fastener in a critical joint is clamped with the precise, engineered force.
- Lightweight Aluminum Construction: Fabricated from high-strength 2024-T851 aluminum alloy, providing an excellent strength-to-weight ratio. This makes it a preferred fastener for reducing the overall weight of the airframe compared to traditional steel nuts.
- Red Anodized Finish: Finished with a red anodize coating per MIL-A-8625. This finish provides corrosion resistance and serves as a visual identifier for the aluminum alloy material.
- Industry Standard: As a standard part used and specified by Textron Aviation, it guarantees full traceability and conformance to the demanding quality and performance characteristics of the Hi-Lok system for primary structural applications.
Technical Specifications
- Part Number: HL75-6A
- Component Type: Hi-Lok Tension Frangible Hex Collar
- Material: 2024-T851 Aluminum Alloy
- Finish: Red Anodized
- Nominal Pin Diameter: For use with -6 (3/16 inch) Hi-Lok pins.
- Thread Specification: .1900-32 UNJF-3B
- Installation Tool Requirement: Hi-Lok installation tool with a hex key to hold the pin stationary while the collar is tightened.
Aircraft Compatibility
Hi-Lok tension fastening systems, including the HL75-6A collar, are used extensively in the assembly of modern aircraft where high-strength, fatigue-resistant joints are critical. They are found across the Textron Aviation product line.
- Common Aircraft Platforms:
- Textron Aviation (Cessna & Beechcraft): Citation series business jets, King Air series, and other high-performance platforms.
- Universally used by other major airframe manufacturers like Boeing and Airbus.
- Common Applications:
- Primary fuselage and wing splice joints.
- Attaching engine pylons and wing-to-body fairings.
- Securing critical fittings and brackets that are subjected to tensile loads.
Applications
The HL75-6A collar is the specified component for creating permanent, high-strength structural joints under tension:
- Fatigue-Critical Structures: The consistent, high preload achieved with the Hi-Lok system is essential for maximizing the fatigue life of a structural joint under tension.
- Replacement for Heavy Hardware: A key component used by engineers to replace heavier traditional nuts and bolts, reducing airframe weight without compromising structural strength.
Why Choose HL75-6A?
The strength and reliability of an aircraft's structure is dependent on the integrity of its fastened joints. For joints under tension, the ability of the fastener to maintain a high clamp load is paramount. The Hi-Lok system with the HL75-6A tension collar provides a scientifically controlled method for achieving this clamp load. Using a genuine, traceable HL75-6A ensures you are installing a component with the certified material strength and precise engineering required to guarantee a safe and airworthy structural connection.
Order Your HL75-6A Hi-Lok Collars Now
Build and repair your aircraft structure with the precision and reliability of the Hi-Lok fastening system. Visit Airparts.aero to order your genuine HL75-6A tension collars today.
In aerospace structures, a joint can be designed to primarily handle shear loads (forces acting parallel to the surface) or tension loads (forces acting perpendicular to the surface, pulling the joint apart). While a standard shear collar (like an HL86) is sufficient for shear applications, a tension application requires the HL75-6A. The HL75-6A's larger diameter and integral washer face provide a greater bearing area. This larger area is critical for distributing the high clamp load of the torqued collar onto the structure without exceeding the material's bearing strength, which could otherwise cause crushing or deformation of the skin, especially on softer aluminum or composite surfaces. This makes the tension collar essential for maintaining the integrity of the joint under significant pulling forces.
Note: This is a flight-critical structural component. It must only be used where specified, in conjunction with the corresponding Hi-Lok pin of the correct diameter and grip length. Installation requires specialized Hi-Lok tooling. The sheared-off hex portion of the collar is discarded. These collars are not reusable.