How to remove a broken screw

We bought an antique office chair to restore. Its main components are made of walnut and it will look great once it has been cleaned up.

Some of the screws that secure some pieces together were missing, and upon closer inspection I found it was the screw-heads that were broken off – the body of the screw remained in the holes.

Screw ‘extractors’ (see here for an example) are designed to work on stripped screw heads. As I have only the body of the screw available the surface area to work with is simply too small for an extractor (if you can get them to work at all).

Time to dig

So the only option is to dig a mortise around the screw to expose it, and then come in with some needle-nose pliers and unscrew the screw body from the wood. Some points to note:

  • Be CAREFUL using chisels near metal parts. It’s very easy to chip the edge you’ve just sharpened….
  • I used an awl to scrape material from around the screw to save my chisel from harm.
  • I had to excavate quite a depth around the screw before it was loose enough to unscrew. The reason it snapped in the first place is because it is in there so tightly (probably no pilot hole was drilled prior to the screw being forced in).
  • The needle-nose pliers took a beating, too. It is hard to get a good grip for twisting the screw out.

Plug the hole

Once the screw was out, I used scrap walnut to create a square plug for the hole. The plugs have a friction fit but are still glued in place and flush-cut to the surface. I drilled a pilot hole in the centre of the plug for the new screw to go in.

All in all, I had five of these broken screws and the procedure took some time to do. I’ll post about the remainder of the restoration sometime soon. They don’t make ’em like they used to…

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