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The brace is one of the oldest boring tools still used today. It consists of a chuck to hold different bits, a U-shaped shaft with one handle at the bottom of the U, and a pad at the end opposite the chuck. Pressure is applied to the pad, usually by leaning on it, and the handle is cranked to drive the bit. Modern braces use special square shanked bits, designed to provide great torque, and sometimes have a ratchet mechanism to allow them to drive screws or drills in tight quarters. Most braces come in two or three sizes, the difference being the offset of the driving handle, with a larger offset providing more power.
Crank Drill:
Also called an egg beater drill for its resemblance to the mechanism used in old egg beaters. This is the usual tool for holes under 1/4" in size. The crank provides less power but more speed for powering smaller bits, which are often stored in the handle.
Yankee Drill/Driver:
This is a rare but fascinating little gizmo, ideally suited for "shooting" small screws. The design is centered around a 8"-15" metal shank with spiral grooves milled in it going both clockwise and counterclockwise. The shank slides in and out of the body of the tool and is pushed out of the body by a spring in the handle. The tool is used by fitting a bit into the end of the shank, then moving the handle up and down in a reciprocating motion. The beauty of the tool is that on the driving stroke, the handle is being pushed down, applying both the torque and the driving pressure. A ratchet mechanism allows both driving and withdrawal of screws, and special drill bits can also be fitted. This is a very compact tool; with the shank locked into the body, it is only 12"-18" long by about 1 1/4" in diameter at the handle.
This is a very simple tool for starting screw holes, especially in softer woods. It is simply a screw pointed twist drill with a T-handle permanently attached. Gimlets are available for most screw sizes.
Twist Drill:
This is by far the most common drill type today, though not the best suited for woodwork. It may be found in sizes ranging from ~1/64" to 1" and sometimes even larger. They come in various materials, including the common high speed steel, cobalt steel, titanium nitride coating, black oxide coating, etc. These bits are designed for drilling in metal and plastics, and do not cut wood fibers very cleanly, nor do they stay perfectly centered when drilling in wood.
Brad Point Drill:
This is what you get when you modify a twist bit design to suit woodwork. It has spiral flutes like a twist bit, but has cutting edges shaped to cut wood cleanly and efficiently, and a spur to keep the bit running on center. These bits produce much cleaner holes with minimal tearout on the exit side, and all tearout can be eliminated by using a backer board. These bits are slightly more difficult to sharpen than standard twist drills, but it is still possible to do a decent job freehand on a bench grinder -- after a little practice, of course.
Spade Bit:
This is the simplest of all drill bits, as it is just a flat piece of metal with a round shank, ground with a large center spur and two cutting flutes. These bits don't cut as cleanly as some of the more expensive styles, but they are an inexpensive way to drill a variety of hole sizes 1/4"-1" in diameter. One other advantage is that these bits can be modified to drill tapered holes, as for candle brackets.
Augers are available in sizes ranging from 1/4" up to 3" when using expandable bits. They are usually used in a brace, as great torque is necessary to drive the larger sizes. They have a threaded center spur, which keeps the bit running on center and pulls it into the wood. There are three thread styles; coarse, medium and fine lead, depending on the hardness of the wood and the degree of smoothness required in the hole. For cutting, augers make use of one or two cutting edges formed in the flutes, similar to a brad point bit but with extra side spurs to cleanly sever wood fibers. As mentioned before, special expandable bits having one main cutting edge are available, and one bit with two intercangeable cutters can cut holes from 7/8"-3" in diameter, with an infinite number of sizes in between.
Yankee Style Drill:
The yankee drill is described above; here I describe the drill bits for it. They have one end cut to an odd shape to lock into the shaft of the tool, and the other end is sharpened like a twist drill, only the flutes of the drill run straight up the sides, rather than spiralling around. The drill is sharpened to a less aggressive point to limit the bite it takes due to the way the yankee drill operates.
The ultimate in simplicity for making small diameter holes. This is just an awl with a tapered shank to fit the taper on the screw, and the shank is milled square. To use it, you press it into the wood and twist; the square shape is very effective at pushing the wood out of the way, leaving an excellent starter hole. It also works quite well in locating center points for twist drills.
This is the preferred bit of chair makers. It is shaped like a half cylinder with a semi-spherical cutting edge. It drills a hole with a rounded bottom, not flat bottomed like most bits. The rounded bottom makes for stronger leg joints in chairs and reduces tearout on exiting the back side of the wood.
This bit cuts a tapered hole for the head of a countersunk screw. Many styles of countersink bit are available, some can also be used on brass and aluminum, and some will also drill a counterbore for the screw head.
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