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Drills and Bits
Written by Elizabeth Wood
Editor In Chief, United Home Improvement


Electric drills are a wonderful tool to have around the house; however, they aren't so wonderful without their bits. A drill is a tool with a rotary drill bit used to put holes through material. There are several different types of drill bits. Each type is specially made to drill through specific things. With all bits combined, you will have a tool that will drill through just about anything. However, to drill a suitable hole in any material, the correct type of drill bit must be used. Below is a list of the most common drill bits used.

Twist Drills:

The twist drill is also sometimes referred to as the Morse drill. Morse comes from the name of the fellow that invented the twist drill. The twist drill is the most common type and it consists of a cylindrical metal rod with a bit or drill having deep helical grooves. The drill bit is held by the drill at one end, in the "chuck", with the other end being pressed against the target material and rotated. Generally, twist drills are sold in sizes ranging from a sixteenth of an inch up to half-inch diameters and are used on timber, metal, plastics and similar materials.

Spade Bits:

Spade bits are a popular item for boring small holes through wood. Its angled spur design cuts accurate holes cleanly and quickly. A spade bit has a very distinguishable shape to it. It looks a little like a flat shovel with a point in the center of the end. The point is used as a guide when drilling. The bulk of the drilling is great for cutting precise holes through wood, plywood, and some plastics. Spade bits are found in the range between quarter inches in diameter to one and a half inches.

Brad Point Drills:

Brad point drills are a combination of twist drills and spade bits. They are designed for smooth, precision cuts and produce a virtually flat bottomed hole. They are commonly used for cross-grain boring in wood, and other woodwork requiring smooth, accurate holes. They have ground center points to hold drills on target during use and two cutting flutes that give quick cutting action, rapid chip ejection and are easy to re-sharpen.

Countersink Drills:

Countersink drills can be used to countersink the top of a hole. They are commonly used to drill pilot holes for wood screws. These drills are tapered at the point, have two adjustable collars to adjust the depth of drill and depth of countersink. These bits tend to be designed for use on soft materials such as timber and plastics, not metals. They are available with fitted handles so that they can be used by hand twisting.

Hole Saws:

Hole saws are a drill which consists of a circular saw blade, used to cut holes in wood, plastics, and a variety of metals, including iron, steel, and aluminum. The hole saw bit is made up of two parts, the mandrel and the blade. The mandrel is a shaft to which the blade is attached. The blade of the hole saw is a hollow cylinder with teeth on its top edge. They are best used in a power drill at low speed.

Forstner Bits:

Forstner bits are specially designed to drill virtually flat bottoms in all types of soft and hard woods. Many agree that for precision holes the best bits are forstner bits. These bits will not chip your wood like other bits. They do not move off center through unusual grain or knots because they are guided by the rim. Forstner bits are moderately expensive. Many jobs do not require this type of bit, but they are great for mounting mini-quartz clock movements, cup hinges, and mounting hinges that must be recessed into a round hole that extends only partway through a door stile.

Masonry Bits:

Masonry bits are designed for drilling concrete, stone, brick, plaster, quarry tiles and other masonry materials that would damage other drill bits. The cutting tip is made from tungsten carbide bonded to a spiraled steel shaft. Generally, they are used in a power drill; although they can be used in a hand brace. Masonry bit sizes range from 4 to 16mm.

Other Drills:

Many jobs around the house require a hole of some kind to be drilled and the bits listed above can be used for most of those jobs. For all other jobs, several other drills should be considered. Other drill types include corner bits, mixed bits, glass bits, tile bits, and wood auger bits.

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