How to Install a Helicoil

Written by c.l. rease
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Stripped and broken threads are a fact of life in auto repair. Even if the threads are damaged beyond a simple re-tap, the mounting hole can still be fixed and reused. Helicoil inserts allow you to replenish the threads, even if the threads are completely removed from the bolt hole, a common occurrence with aluminium threads. The procedure for installing a Helicoil is the same for all hole diameters, and everything you need to perform the thread repair is included in a Helicoil kit.

Skill level:
Moderately Easy

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Things you need

  • Drill
  • Helicoil Kit
  • Thread lock
  • Hammer

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  1. 1

    Remove the bolt from the stripped threads. If there is a broken bolt remaining in the hole, use a bolt extractor to remove the bolt from the threaded mounting hole.

  2. 2

    Place the Helicoil recommended drill bit for the hole size being repaired into the drill. Drill the hole deep enough to accommodate the Helicoil insert and the bolt that is going to be threaded into the hole.

  3. 3

    Tap the drilled hole with the tap specified in the Helicoil kit. Keep the tap straight with the hole. Turn the tap in a clockwise motion to thread the hole. Turn the tap until it binds, back the tap up a 1/4 turn; continue to thread the hole in a clockwise direction. Run the tap to the bottom of the hole. Do not try to exert heavy pressure on the tap. Carbide taps are brittle and can easily be broken off in the hole.

  4. 4

    Thread the Helicoil on the mandrel of the supplied Helicoil installation tool. Liberally apply thread lock to the Helicoil insert. Place the Helicoil insert into the hole. Thread the Helicoil insert into the hole until it rests at least a 1/4 turn below the surface of the metal having the stripped threads repaired. Remove the insert tool by turning it counterclockwise.

  5. 5

    Insert the tang break-off tool into the repaired hole. Hit the end of the tang tool with a hammer to snap off the tang. If you are repairing the threads in a large hole, reach into the hole with a pair of needle nose pliers and grasp the tang. Twist the tang back and forth until it breaks free of the Helicoil insert. Allow the thread lock to set-up before re-installing a bolt into the repaired hole.

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