Woodworker's Journal 2010-34-2, страница 56
Shop Test Countersink Options for Woodworkers Bv A.J. Hamler Whether it's achieving the clean look of a flush-set screw or creating perfectly plugged screws, a reliable countersink is a workshop must-have. Here's a preview of what's available. ^ ivww. woodwofKorstournat.cotr) BB Xquik-unk Quik-Link takes you directly to the web page on which these products appear! No navigation necessary ... just go to www.woodworkersjournal.com and click on the Quik-Link icon shown above. For utility shop furniture or other quick-and-dirty projects — especially temporary items — we often don't care much about the screws. They can be visible or not, proud of the surface or not; sometimes, it just doesn't matter. But for most of our work, if a screw is going to be visible we want it to look good, seated smooth and flush with the surrounding surface whenever possible. Sure, you could forcibly drive a flathead screw Hush, but that almost always tears the wood surface fibers and looks terrible. In hardwood, you might not even be able to set the screw flush. This is where countersinking (or its close relative, counterboring) comes in. When you top off a pilot hole with a countersink, the screw head seals perfectly: all its surfaces contact the wood with the same amount of force, making for a strong attachment and a clean look. When we want those screws to disappear entirely, a properly sized deep-drilled countersink can accept a wooden plug that can then be cut and sanded flush for a smooth surface and an accented appearance. Handling these tasks, and more, is the job of a dedicated countersink. But there are a lot of them out there: one piece or a combination of drill bit and countersink, single- fluted or with multiple (lutes (or none at all) and a wide range of chamfer angles make for tricky selection. As with just about all woodworking tasks, countersinks work best when correctly matched to the job at hand. Types of Countersinks One-piece countersinks come in two main flavors, the most commonly recognized being a fluted countersink, which has a short shank with an elongated cylinder topped with a conical tip. (The shape always reminds me of the old Apollo command module.) The most typical fluted countersink used to have four cutting edges 011 the cone, although one-piece fluted countersinks today more commonly have an odd number of cutting edges — usually one or five. Fluted countersinks come in several sizes, able to cut conical holes intended to fit screws of varying head dimensions. A pilot hole is first drilled for the screw, followed by countersinking the hole to allow a flathead screw to seat flush with the work surface. It's always best to use a countersink with a body diameter that closely matches that of the screw head; using one too narrow won't create a big enough countersink to accept the screw head, and using one too wide runs the risk of creating a crater-sized countersink that completely swallows the screw. A fairly recent type of one-piece countersink called a cross-hole countersink has 110 flutes. Instead of sharpened cutting edges, the bit has a hole bored through the cone at an angle. As the bit spins, the trailing edge of the hole makes the cut. Used the same way as fluted bits (pilot hole first, countersink second), cross-hole countersinks cut very smoothly and remove material quickly, and they excel at ejecting chips as they drill. These bits generally cost a bit more than their fluted cousins. 58 April 2010 Woodworkers Jourruil |
