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Drills and Bits
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.
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 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 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 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
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 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.
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.