Drilling Tips

Compared to using an old-fashioned brace and auger bit, drilling holes with an electric drill and a modern drill bit is as effortless as punching out dough with a cookie cutter. But if you want all your holes to be round, straight and at the proper angle, it pays to know a few good drilling techniques.

Starting a Hole
When boring holes in metal, twist drill bits rarely stay put on the spot you've marked. You can keep the bit from skittering around by creating a small dimple with a center punch before drilling. A self-centering punch—a spring-loaded, awl-like tool that you press down on to create a dimple—is a good investment if you frequently drill metal. If you plan to bore large-diameter holes, it's a good idea to make a smaller hole first, then enlarge it to final size. Alternatively, try using Black & Decker Bullet bits, which have special tips that create their own pilot holes as you drill.

Drilling Into Metal
Be careful when drilling holes in thin sheet metal with regular twist drill bits: they can quickly snag on the jagged edges of the hole and grab the workpiece right out of your hand. If you're working on a drill press, clamp the work down to the table. In any case, place a backer board—a protective piece of scrap wood—under the metal. For holes larger than 1/4 inch, use a step drill bit that's specially designed for drilling thin sheet metal.

Getting an Accurate, Perpendicular Hole
The easiest way to drill a hole that's exactly perpendicular to a surface is to use a drill press. But if you must drill freehand, here are a few techniques to assure that your holes don't end up catawampus:

Eyeball bit alignment with a square. Hold or clamp a framing square or combination square on the work surface just beyond the hole, and eyeball the shank of the bit with the square's edge. (It helps to work in front of a light, neutral background.)

Use a drilling jig that mounts the drill to a carriage that slides up and down on two guide rods. The jig's baseplate sits flat on the work surface, allowing you to drill perfectly straight holes every time.

Use a drill with a built-in level. Some drills come with small bubble level vials built into the rear section of the body. Aligning the bubbles with their center marks assures the drill bit is plumb.

Preventing Tear-out
If you want a clean hole on both sides of the wood you're drilling, protect the underside of the workpiece with a backer board. This prevents wood fibers from tearing out as the drill emerges from the other side.

If you're drilling with a spade bit or hole saw, drill only until the bit's center point or pilot penetrates the workpiece. Then stop drilling, back the bit out, flip the work over and finish the hole from the other side.

Making the Right Size Pilot Hole
Pilot holes guide your drill bit into the workpiece and keep it from splitting and . But sizing them can be tricky: if they're too big, the screw's threads will strip out easily or fail to bite; if they're too small, you run the risk of splitting the wood or breaking the screws.

Visually compare the drill bits and the screw until you find a bit whose shank (not including its threads) is just slightly smaller than the shank of the screw. You can also measure the screw shank with calipers, but eyeballing it works for most of us. In any event, pilot holes should be slightly smaller in softwoods and slightly larger in hardwoods. For example, if the screw's shank measures 1/8 inch in diameter, you'd drill a 7/64-inch pilot hole in pine or fir and a 9/64-inch pilot in maple or oak.

Traditional wood screws are tapered along their length, so you'll get best results by making pilot holes for them with special pilot drill bits. These come in sizes that correspond to standard screw sizes such as #6, #8 and #10.

To make screwing easier and prevent wood splitting and screw breakage, wax your screws before driving them. Drag the threads across a chunk of paraffin or an old candle to lubricate them. Avoid using soap, though; it can cause steel screws to rust.

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