how to remove hi lok fasteners

Introduction

When working with airplanes or other complicated machinery, you may encounter rivets or bolts that hold different parts together. One such fastener is a Hi-Lok fastener- a popular feature of aerospace assemblies. You’ll often find them in different structural systems, like wings, fuselages, landing gear, control surfaces, and engines. These fasteners may require removal for repair, replacement, modification, or upgrade. But how do you remove them without damaging the surrounding area or the fastener itself? Here are some tips to help you safely remove Hi-Lok fasteners.

Understand the Hi-Lok Fastener

Before removing Hi-Lok fasteners, you need to know what they are and how they work. Hi-Lok fasteners are non-threaded fasteners that come in different materials like titanium, steel, and aluminum. They use a threadless collar that shrinks around the pin, locking it in place. The collar is tightened with a hydraulic tool that stretches it past its elastic limit, increasing mechanical contact friction between the collar and the pin. That makes the collar tough to remove unless you know the right techniques.

Prepare Proper Tools

Removing Hi-Lok fasteners requires specific tools to back out the pin while keeping the surrounding area intact. The tools should fit the pin and fastener body precisely, without scratching or damaging them. Here are some suggested tools that you’ll need:

1. Hi-Lok removal tool: This tool works together with a ratchet or a torque wrench to turn the pin and back it out. The tool has a hollow center that allows the pin to slide through.

2. Sealant removal tools: Hi-Lok fasteners usually have sealants around them to provide additional strength and prevent corrosion. You’ll need special tools to remove the sealant without damaging the pin or the collar.

3. Pin and collar cutters: In some cases, you may need to cut the pin or the collar to remove them. Use a specially designed cutter to avoid damage to the surrounding area.

4. High-speed drill: Sometimes, the pin may get stuck or refuses to back out. Use a high-speed drill to drill out the pin without damaging the surrounding area.

Prepare the Work Area

Removal of Hi-Lok fasteners involves the possibility of metal shavings or debris. Therefore, you’ll need to prepare the work area. You’ll want to clear out any flammable fluids or gases nearby, and cover the surrounding area with protective heat blankets or fire-retardant materials. Place a catch pan underneath to collect any debris, and avoid using excessive force when removing the pin to prevent nicking the pin or collar.

Follow Proper Procedure

Once you know what specific tools you’ll need, and you’ve prepared the work area, you’re ready to proceed with the Hi-Lok fastener removal. Here are some general steps that you should follow:

1. Identify the location of the Hi-Lok fastener and inspect the surrounding area for damage or corrosion.

2. Clean the work area thoroughly, to remove any debris, sealant or grease from the fastener.

3. Clamp on the Hi-Lok removal tool onto the fastener body and turn the pin counter-clockwise to release it. Use heat to soften the sealant if it's giving you difficulty. If the Hi-Lok tool breaks or gets stuck, stop trying to remove the fastener.

4. After you remove the fastener, inspect the area again to ensure no corrosion or scratches have occurred. Apply corrosion protection if necessary.

Conclusion

Removing Hi-Lok fasteners is challenging, but with the right knowledge, tools, and procedures, it can be done successfully. Remember to never apply excessive force when removing the pins to prevent any damage to the fastener, surrounding area or the mechanic working on the aircraft. If you're feeling unsure or need more guidance, request assistance from a professional mechanic or your aircraft manual.