Tuesday, August 28, 2012

Tuesday Tool: Screwy

The last Tuesday Tool was kind of old-fashioned; today's is ancient and at the same time totally high-tech.  It's the TEKS Wood-to-Metal self-drilling, self-tapping screw.

So here's the problem: I wanted to attach a piece of wood to quarter-inch thick metal.  Until a week ago, I would have thought it necessary to drill a hole in the wood and drill a hole in the metal and then tap some threads in the hole in the metal.  If I did that, I'd need to make sure that the holes lined up exactly, and that the hole in the wood was a size larger than the hole in the metal so the threads didn't engage the wood, and I'd have to exercise some care in tapping threads.  A week ago, I was introduced to this screw. 

The tip of the screw is hard metal shaped into a bit.  It's the first thing the wood feels, as it rapidly gets holed.  The next thing the wood feels is a pair of "ears" behind the bit; these widen the hole in the wood so that the wood never feels the threads on the screw.  When the tip of the screw has traveled through the wood and hits the metal, it keeps on drilling.  When the ears hit the metal, they snap off and become lodged in the wood.  The first bit of threading is grooved to act as a tap, and it cuts threads into the metal.  Then, the threads bite into the metal, and pull the head--and ultimately the wood--snug against the metal.

It's brilliant: you clamp your wooden post into place on the metal, put one of these screws on your drill, and away you go--and in a few seconds, your post is firmly in place.  It's ancient technology--the screw is simply an inclined plane, one of the classical "simple machines."  It's high tech--I assume some metallurgical expertise had to go into making the bit and tap parts hard enough, and the screw precise, and it would be useless without power tools to drive it.  Brilliant--to whoever designed this, Bravo/Brava!

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