Gilles' Outlet

February 4, 2008

Extracting a Broken Screw

Filed under: Carpentry — Gilles @ 5:38 am

A broken screw is extracted from a piece of wood.

 
Skill Level: 2 (Basic) Time Taken: About 5 minutes

Almost all building contractors and auto mechanics have been exposed to broken screws. This article explains how to extract the broken screw without damaging the piece it threads into. While the example of a wood screw broken in dimensional lumber is taken, techniques described below can be used to remove virtually any piece of hardware threaded into another material.

The broken screw of interest. The head fell off when I tried to remove the hinge from a door jamb. As far as broken screws go, it is fairly bad because:

  • The screw must get out otherwise the hinge will not be strong enough to hold the door,
  • It is not practical to replace the whole jamb,
  • A large part of the broken screw is still inside (I could judge by the head of this wood screw that it was probably  8 x 2 screw) so I can’t just use a smaller screw and ignore the problem,
  • The broken piece is not visible from outside and it is about 3/4” deep inside the material,
  • The door jam must not be damaged in any way during the extraction.

In general, extracting a broken screw is done following those steps:

  1. Look for solutions involving discarding the piece into which the screw broke. It usually does not make economical sense to discard the work piece but every once in a while; it is actually an option,
  2. If the end of the broken screw is visible and protrude outside of the material by at least 1/16” or more, use a hack saw or a rotary cutting tool (aka "Dremel") to cut a groove in the broken screw shank. A flat screwdriver can then be fitted into the groove and the screw can be removed,
  3. Consider chipping material around the screw hole to expose the broken screw shank and apply technique described in 2,
  4. If everything else failed, a special tool called a "screw extractor" can be used. This is the purpose of this article.

Left: Tools for extracting the screw. From left to right: a 5/64” drill bit, a #1 screw extractor and a "T-Handle".

 

Right: The screw extractor has a square drive meant to be inserted into the T-Handle.

The chuck is tighten until it holds the screw extractor tight.

Left: The business end of the screw extractor. It is basically a spiral with threads going counterclockwise. Regular screws or drill bits have threads going clockwise.

Driving screws clockwise will cause them to penetrate the material. The screw extractor needs to be turned counterclockwise in order for its threads to grab.

Right: A regular screw (top) compared to the screw extractor.

This difference makes the screw extractor capable of extracting broken screws quite effectively.

Screw Extractors are used as follows:

  1. First, a small hole is drilled into the broken shank of the screw,
  2. The screw extractor is then threaded into the hole previously drilled and turned counterclockwise (aka from right to left),
  3. Since driving the extractor counterclockwise causes the extractor to bite into the screw, it is now possible to drive the broken screw out using the screw extractor.

Screw Extractors come in several size and are commonly referred to by a number. For instance, this article features screw extractor #1, the thinnest of all common extractors. Screw extractors are available at most home centers and well supplied hardware stores. Choose the screw extractor which best matches the size of the screw to remove.

Every extractor calls for a specific hole size. The #1 extractor is usually used with a 5/64” drill bit as shown in this article.

Left: I drilled a 5/64” hole into the broken shank of the screw. I tried to drill in the exact alignment of the shank but this was difficult because I could not see the shank. 

After about 45 seconds, I had drilled a hole which I estimated to be about 1/8” deep.

Right: I threaded the screw extractor into the hole and turned counterclockwise (from right to left).

I felt the tool engaging into the screw and starting to drive it out as I turned.

Left:  After about three full turns, the screw appeared outside of the wood. It came fairly easily. I continued turning the extractor until the whole screw was completely out.

Right: The extracted broken screw still attached to the extractor.

The more you turn to remove the screw, the more the extractor tightens its grip into the hole.

I after only 5 turns, I had to hold the broken screw with a pair of pliers to remove it from the extractor.

A close up of the hole drilled into the broken screw. It is about 20% smaller than the shank of the screw.

NOTE: It is important to manually drive the screw extractor instead of using a power tool like a drill or an impact wrench. Using a power tool could cause the screw to break again or worse, the screw remover itself to break.

Hand driving the tool allows the operator to feel if the broken screw is correctly engaged and to make the necessary corrections as required.

It is sometimes necessary to extend the size of the T-Handle with a piece of metal pipe in order to increase the torque provided to the screw extractor. In this case, proceed very carefully to avoid breaking the screw and / or the screw extractor.

Tools Used:

  • Cordless Drill
  • Screw Extractor (#1) and T-Handle
  • Drill Bit

Materials Used:

  • None

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3 Comments »

  1. I have found that using a drill you can tighten the chuck of the drill hard around the exposed portion of the broken or stripped out screw then run the drill slowly counter-clockwise to back out the screw.

    Worked for me.

    Comment by Kevin Donovan (@kvan) — December 4, 2011 @ 7:39 am

    • Fantastic advice! Worked for me too. Your advice has really helped me out. Thanks so much for sharing.

      Comment by Julia B — January 7, 2013 @ 1:29 pm

  2. [...] because the extraction process is more fragile than the normal insertion of a screw.Check out Gilles’ Outlet for a detailed writeup of the process explained above. — Answered by Jeff FerlandAnswer: The [...]

    Pingback by How To Remove Screws With Stripped Heads | Lifehacker Australia — April 13, 2012 @ 1:56 pm


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