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Project Difficulty:
Moderate
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It is important to choose the correct drill bit for the task at hand. Here are some of the options.
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1.
Bits for Drilling Holes
Twist Bit (Three-Point Wood Bit)
The most common type of drill bit, the twist bit, has three points: a sharp central point that makes the bit easy to position for accurate drilling, and two spiral-shaped cutting edges that lift chips out of the hole as the bit turns. This type of bit gives fast cutting action and makes clean, sharp holes. Though suitable for drilling hard or soft wood, laminate, and plasterboard, high-speed steel (HSS) twist bits are available as well, for drilling soft metals and other materials. Designed for use in both hand and power tools. Common sizes range from 1/16 inch to 1/2 inch. (Figs. 1 & 2)
Spade Bit (Flat Wood Bit)
This bit is for drilling larger diameter holes in wood. It is a wide, flat blade with a triangular pilot bit in the center, and is designed for use with rotary action power drills. It's ideal for hard or soft woods, chipboard, and floorboards. Some spade bits have outer spurs that cleanly score a hole before blade contact. Cutting diameters range from 1/4 inch to 1-1/2 inches. (Fig. 3)
Brad Point Bit
This bit has a central spur that keeps the bit on center and sharp outer spurs that score the hole size before removing wood, thereby preventing the wood from splintering. Brad point bits are suited for doweling, and their flutes enable quick removal of material, providing clean boring of holes in either soft or hard woods. Special titanium coatings improve the penetration and extend the life of brad point bits. Available in sizes from 1/8 inch to 1/2 inch. (Fig. 4)
Auger Wood Bit
This bit is suitable for all types of wood and is used primarily for cutting deep holes. It has a central, self-feeding screw that pulls the bit into the wood for precision drilling, and a deep throat and double twist design for fast debris clearance. Works in either a rotary power drill or a brace and bit. Tempered carbon steel keeps a sharp edge. (Fig. 5)
Forstner Boring Bit
These bits remain centered while cutting. Designed for efficient removal of debris, their precise edges drill clean holes in both soft and hard woods. Forstner bits are often used to cut partial arcs, holes in end grains, and pocket holes. The shaft fits most portable drills and drill presses. Sizes range from 1/4 inch through 1-1/2 inches.
Cup Hinge Boring Bit
This bit cuts holes for cup hinges, cylinder locks, and spindles. A center point prevents the boring bit from "walking." Precision edges provide smooth cutting and quick removal of chips. It fits most drill chucks. A titanium tip lasts longer and improves penetration into both soft and hard woods, while a carbide tip extends the life of the bit beyond that of conventional steel. This bit can be used with composite as well as solid woods and laminates.
Masonry Bit
High-speed bit having a brazed tungsten-carbide tip. A tough, general purpose bit, available in a variety of sizes, used for drilling holes in concrete, concrete block, cinder block, brick, and stone. Extension sleeves allow deeper drilling with rotary hammer action drills. Specially designed steel (SDS) masonry bits also come with twin spiral tips for effective debris removal, especially for cutting into structural masonry. These heavy-duty bits can be used with either electro-pneumatic or rotary hammer drilling machines. (Fig. 6)
Glass Bit
This type of bit has a diamond-lapped spear shaped tip for smooth drilling of larger holes. Its copper alloy, brazed tungsten-carbide tip provides superior performance and extended life. Can be used with either a hand brace or rotary power drill.
Drill Rasps
For enlarging or shaping holes in plastic, metal, or wood. This type of bit is used to form irregularly shaped holes or to enlarge existing holes.
Drill Saws
These cut irregular contours and enlarge blind holes. Edges of high speed steel are hardened for long life. They are designed for use on wood, soft metal, plastic, and rubber.
Hole Saw
This consists of a circular rim with saw-toothed edges and a centered, removable pilot bit. It is used for cutting large holes, such as those needed for door hardware or plumbing pipes. It can be used in electric or pneumatic tools, vertical drills, lathes, milling, and other machine tools. You can purchase hole saws that can cut through case iron, stainless steel, aluminum, brass, plastic, or, of course, wood. Common diameters range from 1 inch to 4 inches. (Fig. 7)
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2.
Bits for Screw Holes, and Driving and Setting Screws
Today, portable drills are used as often to set screws as to drill holes. In fact, a wide range of drill bits are designed solely for making screw holes, and driving and setting screws.
Slotted Blade Driver Bit
This is for driving regular, slotted screws. Shanks are typically hexagonal and insert 1 inch into the chuck. Threaded 1/4-inch screw shank drives are also available. Slotted blade driver bits are difficult to keep positioned in the screw slot, but can be obtained with a self-centering outer sleeve that helps keep the bit from slipping.
Phillips-Head Driver Bit
These bits are for driving Phillips-head screws. They come in a variety of shank sizes, both square and hexagonal, and as insert, power, or threaded bits. Some are reversible, with a different-sized bit on each end. They are available in standard hardness for soft screws, and extra hardness for driving sheet metal or case hardened screws.
Square Recess Driver Bit
Designed for driving screws with a recessed square in the head, these bits fit tightly into the screw head, resulting in minimal slipping. Available as insert or power bits, with hexagonal shanks.
Socket Head Driver Bit
These are similar to a square recess driver bit, except that the recess in the screw head is hexagonal. They are commonly used for metal ductwork and metal roofing, and are available as either an insert or power bit in a variety of sizes.
Miscellaneous Driver Bits
These include driver bits for virtually every type of screw head imaginable, from Frearson, torx, pozidrive, and tri-wing, to quadrex, spanner, and clutch-style heads.
Countersinks
These bits are manufactured from special alloy steel and have hardened edges that extend the life of the bit. They are used for pre-drilling holes to countersink screws in wood, soft metal, plastic, and rubber, and may also be used for deburring and chamfering.
Screw Setters
These are precision tools used for drilling, countersinking, and counter-boring all at once. The drill bits are high speed steel (HSS) and are able to grip screw threads securely. They can be used with portable drills and drill presses on either soft or hard woods. Triple fluted and tapered bits allow for quick debris clearance. Countersink bits permit flathead screws to be seated level with the surface of the wood. They can be adjusted for the depth of the hole. Drilling deeper establishes a counterbore to accommodate a wooden plug. Sized for #6 through #12 wood screws.
Screw Hole Bits
These bits are designed for countersinking to make the driving of screws less difficult. They can also be used to counterbore holes for wooden plugs and can be adjusted for depth. Usable in most drill chucks, and appropriate for all woods, screw hole bits come sized for #6 through #12 wood screws.
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