h a l f b a k e r yThe embarrassing drunkard uncle of invention.
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The ordinary type of wood screw, when used with fine wood, typically needs a "pilot hole" to be drilled into the wood before the screw is applied.
The pilot hole accommodates the "shank" of the screw, which is its solid metal core, and which has attached to it the helical screw-thread that actually
bites/grips the wood. Without a pilot hole, fine wood can acquire a large and ugly crack when the shank is forced into it.
An auger is typically a type of drill bit, but its most distinguishing characteristic is that it is basically a helical screw-thread without a shank/core. Or at least its core has minimal diameter. If you compare an ordinary wood screw with the same diameter of the type of screw made to penetrate gypsum board ("drywall"), you will notice that the helical screw-thread is rather wider on the drywall screw than on the wood screw. Or you could simply say that the shank/core is smaller.
An auger screw would reduce the shank/core as much as possible, and therefore would consist almost entirely of the thin helical screw-thread. And therefore, because the shank has such a small diameter, no pilot hole need be drilled, when using this type of screw with fine wood.
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This is pretty much Baked ... screws for use in uPVC typically have "self-cutting" tips and a very thin shank. |
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I think you might have difficulties with your screws breaking if you eliminate the shank. Drywall screws with a narrow shank don't need to be as strong because the drywall is soft and the screws are not going very deep into the realatively soft wood framing. Still I frequently break the heads off of drywall screws. When I hear "fine" wood, I immediately think hard wood, which sounds like trouble to me. |
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When I read the title, I thought you were going to propose a screw with a built in auger to self tap a hole. One way that might work would be to have a hollow shank with the auger on the inside. That could be pretty expensive to manufacture, and I'm not sure what the best way to allow wood shavings to escape would be. A hole through the top of the head would require a different driver and might not look good. A hole in the side near the top might make the hollow shank too weak. |
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// I think you might have difficulties with your screws
breaking if you eliminate the shank. // |
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I don't think they'd break-- I _know_ they would. The big
reason why auger-style drill bits are only used in fine
woodworking (and mainly in hand-working at that) is that
they have very little shear strength. If auger-shaped screws
were used to build, say, a bureau or cabinet, they would
snap the first time somebody gave it a hard bump with
their hip. |
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It's an elegant concept, but it won't work with conventional
materials. |
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// I frequently break the heads off of drywall screws // |
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That's because drywall screws are made from fecking pot
metal more than it has anything to do with the shank. |
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