Big Bores – Best for Drilling Large Holes
If you’re like most people, it’s a safe bet that nearly every time you drill a hole in wood, you’re using the wrong tool. How so? Because most of us – and that includes me – do our drilling with the twist drill, a bit actually designed for drilling metal.
In practice, twist drills work pretty well in wood, at least in the smaller sizes. But when you start boring holes much over one-quarter inch in diameter, the twist drill’s wood-drilling weakness really start to surface.
They skid around when you try to start a hole. They cut roughly and splinter your work when they come out the back side. They clog with chips when you drill deep, then overheat, lose their temper and become dull.
The moral? If you need to drill big holes – to hang a closet pole, run plumbing or wiring, set a chair leg, or whatever – you need something other than a simple twist drill.
What you do need depends on the type of work you are doing, and how much money you care to spend.
For holes from 1/4-inch on up to a full inch, brad-point bits are a good bet. These look a lot like twist drills, but they have center points and cutting spurs at the rim of the tip. The sharp center point keeps them from wandering when you start a hole, and their twin knife-like cutting spurs shear through wood to produce a neat, clean hole.
You can buy reasonably-priced sets of seven or so bits in the 1/8- to 1/2-inch size range for about $15. These are not the highest quality brad-points available, but they do a decent job for the homeowner.
Once you go above the half-inch size, brad-point bits start to get expensive. You can expect to pay $15 or more per bit in these larger sizes, so it pays to buy these big bits only as you need them.
If you are looking to save money on bits up to about 1 1/2 inches, spade bits (at about $2 a shot) are a good choice. As their name implies, they resemble flat, square-nosed spades.
Don’t count on a spade to cut a perfect hole, at least not if you use them freehand. In a drill press they can produce a fairly clean hole, but otherwise they often bore rather roughly. Often the holes they produce are not perfectly round. In many cases, however, this makes no difference. Running wiring or pipes through house framing, for example, doesn’t require an award-winning hole.
If you do want smooth, round holes, the Powerbore bit covers the same range of sizes as the spades, and does a much neater job. This better performance comes to a price of around $10 a bit. I use Powerbores for most of my drilling in the 1/2- to 1 1/2-inch range because they do a good job at a reasonable price.
They are not perfect for all tasks, however. If you want to drill a blind hole (one that doesn’t go all the way through the work) to take a chair leg, for example, a Powerbore is not your bit. It’s long center spur will probably poke through and come out the other side of your work. It’s also hard to start a hole at an angle with a Powerbore.
If you want to drill flat-bottomed blind holes, or to bore into stock at an angle, the Forstner but is your baby. A Forstner can also drill overlapping holes to form a pocket or mortise, and it can drill a semicircular hole along the edge of your stock.
Drawbacks? Forstners cost about $15 in smaller sizes such as one-quarter inch, and can go up to $20 or more in sizes over an inch. Forstners are also best used in a drill press, or at least with a drill guide. In fact, most have half-inch shanks, so you couldn’t use them in your 1/4- or 3/8-inch power drill even if you wanted to.
Monster holes: Once you get over 1 1/2 inches, it’s probably best to use a hole saw. These come in two types. One has an arbor that can accept various sizes of cutters resembling cups with saw-tooth rims. An arbor is about $6, and the cups range from around $6 up to $15 or more.
The other type of hole saw features a mandrel with a set of graduated blades bent into circles. One of these with a set of seven or so blades will run you about $15. Though this type is not quite as sturdy as the cup type, it’s adequate for home use.
For the biggest of big holes, turn to the tool shown in the accompanying sketch. This is a fly cutter or circle cutter. It features a steel cutter mounted on a sliding arm that can be adjusted to any size up to around four inches. A fly cutter must be held absolutely perpendicular to your work or the cutter will dig in and stall. This means you need a drill press to use a fly cutter.
If you don’t have access to a drill press, your only solution is to use a saber saw with a fine scroll-cutting blade.
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