Learning Opportunity #1: Off With Your Head!

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Blog entry by Don posted 01-18-2007 11:09 PM 1199 reads 0 times favorited 0 comments Add to Favorites Watch
no previous part Part 1 of Learning Opportunity series Part 2: If In Doubt, Follow the Instructions »

Commenting on one of Gizzard’s first posts, I wrote of my practice of recording my mistakes as Learning Opportunities. In a later conversation with Martin, I got to thinking that this might be helpful material for other LumberJocks. So with this blog, I am commencing a series on LO’s with the intention of about one per month in the series.

Anyone who has used brass screws in their woodworking will have experienced the dreadful “off with your head” scenario.

I was installing brass hinges for the lid of a small box. The box represented many hours of careful work, and I was anxious to get it finished. Perhaps I was rushing things a little as often happens on the home stretch. I had already cut out the hinge mortises by hand. All that remained was to screw the hinges in place.

I’m a bit of a detail freak, so to me it was important to have the diamond shape of each Phillips screw head lined up. That’s eight screw heads considering the lid and body of the box. And then it happened. Without any apparent force, the head of one of the screws that go into the box portion simply detached from the shaft of the screw leaving the shaft buried in the wood.

Now I suspect that many brass screw heads have been epoxied in place. Who would be the wiser? Normally, this would work. A single screw and a little epoxy should hold. But in this case, I was concerned that the weight of the lid be evenly distributed between both hinges and that both hinges have equal structural integrity. My concern arose from the fact that these hinges had their own build in stop to prevent the lid going much beyond 90 degrees. You can imagine that this places more than the usual force on the hinge screws.

So I needed to remove the broken screw shaft that was below the surface of the surrounding wood. I had tried doing that before, and made a terrible mess of the wood. The resulting patch-up looked very amateurish and for all intense and purposes, ruined the piece. I certainly couldn’t back-track without destroying the box. It was already glued up, so replacing the back wall of the box was out of the question.

And then I remembered.

Somewhere I had read of a solution to this. But because I wasn’t certain that I had remembered correctly, or that it would even work, I had to set up a test piece. So I took a screw, drove it most of the way home, but before I did, I sniped of the head of the screw flush with the surface of the wood. Then I took my soldering iron and heated it up until the tip was cherry-red. I then held the tip of the iron against the tip of the broken screw shaft. I held it there until the wood started to smoke. There was no open flame, but the wood around the screw shaft was hot. Then I carefully took a pair of long needle-nosed pliers, and grabbing the end of the shaft while doing as little damage to the surrounding wood as possible, I turned the shaft free from the wood. The heated screw had caused the moisture content of the wood directly adjacent to the screw shaft to become very dry and pull away from the shaft. This facilitated the relatively easy removal of the shaft without much damage to the surrounding wood. And that’s what I needed to prove to myself.

So now that I had tested and proven the theory, I turned to the box and did the same thing. Once the screw was out, I drilled a small whole enlarging the hole left by the removed screw shaft. This I filled gluing in place a hand carved piece of wood, smaller than a dowel. After the glue had thoroughly dried, I sanded the slightly protruding ‘dowel’ flush with the surrounding wood in the base of the mortise. I carefully drilled through the hinge using it as a drilling template. This time I was more careful. I first drove home a steel screw of the same size and thread. I first coated the steel screw with some candle wax to lubricate the thread as it is cut, and prepares the way for the brass screw. I also apply the candle wax to the brass screw.

Oh, I’m still a stickler for lining up my screw heads, but rather than tightening the screw by turning it ¼ more to align it, I get it as close as I can and forget it. (Have a look at the top photo – three of the four screw-heads are aligned, but the upper right one is not.) Also, I use a very small screw-driver which provides minimal mechanical leverage. Those jeweler’s screw-drives work well.

-- CanuckDon "I just love small wooden boxes!"

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