How to Fix a Stripped Aluminum Bolt Hole

A stripped bolt hole indicates a weak spot in a piece of machinery.
A stripped bolt hole indicates a weak spot in a piece of machinery. (Image: Jupiterimages/Photos.com/Getty Images)

Bolts are used as fasteners on machinery in places you will need to access for repairs. Installing a bolt means putting just enough torque on the fastener so that it will hold without leaking or coming loose, but not so much that it strips. Aluminum is used in machinery because of its light weight and low cost. Unfortunately, aluminum bolt holes are notoriously soft and easy to strip. You can fix a stripped aluminum bolt hole with a double-threaded insert that will allow you to reuse the original bolt.

Things You'll Need

  • Lightweight machine oil
  • Drill with bi-metal bits
  • Tap-and-die set
  • Cotton swab
  • Double-threaded insert
  • Ratchet and socket
  • Work gloves
  • Safety glasses
  • Hearing protection
  • Face shield

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Remove the original bolt from the stripped bolt hole. Twist it free by hand and set it aside until you need it later.

Load your drill with a bi-metal bit that is 1/16 inch larger than the existing hole. Twist the chuck on your drill tight with the chuck key on the cord of the drill.

Coat the stripped hole with lightweight machine oil. Coat the tip of the drill bit with the oil.

Hold the drill so that the bit is resting against the stripped hole. Adjust the drill so that the shaft of the bit is at a 90-degree angle to the surface of the aluminum you are drilling.

Squeeze the trigger of the drill while pushing gently against the metal. Do not force the bit into the hole. Let the bit cut through with minimum assistance from you.

Plunge the drill bit into the stripped hole slowly pulling it free before the next plunge to smooth the hole while making it slightly larger than it was before.

Coat the appropriate sized tap from your kit with machine oil. Slowly twist it into the hole while holding it at a 90-degree angle to the metal surface. Take your time and cut the threads straight into the metal.

Move the end of a cotton swab around the inside of the hole to clear away any remaining metal shavings. Coat the cleaned interior threads of the hole with machine oil.

Twist the original bolt into the double-threaded insert. Slip the bolt and insert into your newly threaded hole. Twist it straight into the new threads. Tighten it with your ratchet and the appropriate socket.

Remove and replace the original bolt from the newly installed threaded insert several times to be sure the insert is not coming back out of the hole when you remove the bolt. Install the bolt until you need to access that piece again.

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