Fix a Stripped Screw Hole

Stripping the threads on a screw or machine bolt may seem like the end of that piece of equipment, but the problem can be repaired without too much trouble. What we are going to do is increase the size of the threaded hole by 1/16" in diameter. In this article, we will assume that the original bolt was 1/4" x 20 x 1". Check the "Things You'll Need" section below for necessary tools and parts for replacing the threaded hole and bolt with a 5/16" x 24 x 1".

Steps

Stripped threads in metal

  1. Place the part or equipment containing the internal thread in a vise, or clamp it to a table.
  2. Insert the next size larger bit in the drill and drill out the internal thread parallel/centered with the original hole.
  3. Clean out any shavings with a vacuum, or turn it upside down and tap out the debris.
  4. Place the tap of a size to cut new threads using the tap wrench and oil the cutting part of the tap.
  5. Keeping the tap parallel to the hole, press slightly downward and rotate the tap. The tap is usually tapered so that it will go into the hole before it starts to bite into the metal sides of the hole.
  6. Once the tap is biting into the metal, release the downward pressure and let the tap direct itself down.
  7. Every two or three turns, reverse the tap to remove shavings, and add some oil.
  8. When the thread is completed to the desired depth, clean out the hole and test the new bolt.

Stripped wooden screw hole

  1. Get wooden toothpicks, splinters or skewer to fill hole.
  2. Coat a piece(s) of wood to be inserted using carpenter's glue or wood glue to help secure wood for plugging hole in the stripped screw-hole.
  3. Insert, press-in or hammer/bump wood into the hole.
  4. Use longer and thicker screws if that is possible and seems helpful.
    • Usually you don't have to let the glue dry before installing your screws.



Tips

  • If you can't use a larger bolt to replace the original you may be able to use a screw thread insert repair kit.
  • Make sure the tap's threads per inch is the same as those of the replacement bolt or screw.
  • It is important to keep the drill and the tap parallel to (centered-/straight-in) the existing hole.
  • When you just need to drive the screw on the fly, take a piece of copper wire (14-16 gauge is usually good), and cut it 1/4 inch shorter than the length of the screw shank. Place the wire in the hole and drive the screw in. This works very well, and will do the job in most cases. Almost mandatory when driving screws into brick. Some people use bits of plastic or electrical tape, but copper wire is the best. It is usually not necessary to strip the insulation off.

Warnings

  • If the object you are repairing is a motor or complicated equipment, you should mask off any areas that might catch metal debris from the drilling or tapping.

Things You'll Need

  • 1/4" drill bit
  • 5/16-24 tap
  • 5/16-24 x 1" bolt (replacement)
  • Tap wrench

Related Articles

Sources and Citations

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