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Screwdrivers
Because screws hold by friction, they require
screwdrivers to securely tighten
and loosen
them; there are three styles
to choose from:
- manual screwdrivers - the traditional tool
comprised of a handle and an integrated bit.
When buying a screwdriver, make sure the
grip is comfortable in your hand (check the
diameter), that the shank of the bit is securely
attached (these tend to loosen or pull out
in cheap screwdrivers), and that the bit
is sufficiently strong. Among screwdrivers,
Craftsman from Sears has perhaps the best
reputation and warranty.
- jeweler's screwdrivers - very small manual
screwdrivers with sharp bits designed for
work with jewelry, watches, and eye glass
frames.
- ratchet screwdrivers - an improvement on
the traditional screwdriver, the ratchet
screwdriver allows you to turn a screw without
having to adjust your grip and allows interchangeable
bits.
- electric screwdrivers- similar to an electric
drill, an electric screwdriver is designed
to deliver high twisting power at the push
of a button for faster and easier work. Look
for a high and variable torque.
Types of Bits
Like drills and socket wrenches, screwdrivers
can have fixed or interchangeable bits. With
a manual screwdriver, the bit (i.e., the
tip where the screwdriver meets the screw)
is integrated into the handle and thus not
changeable. As a result, you need a variety
of screwdrivers to meet the most common uses
since screw heads vary in slot design and
size. Interchangeable bit screwdrivers (most
ratchet and electric drives) allow you to
use one handle with a multitude of bits.
The most common bits are for single slotted
or Phillips head (a double slot in the shape
of a plus sign) screws. However, the width,
length, and depth of the slots vary, and
hence there are a variety of bits to match.
When choosing a bit, it is important to match
the bit to the screw accurately so that the
bit becomes an extension of the screw; if
not, you risk deforming the screw head and
making the screw unusable (in which case
you have to drill it out). There are other
types of bits, such as a TORX or spline,
which have various unique patterns.
The length of the bit can be
important, and
this is most often seen with
the manual screwdriver.
A long shank allows you to twist
a screw
that recessed far from where
you can reach,
while a "stubby" allows
you to
work where there is only a small
area for
the handle (another solution
is the use of
an "offset screwdriver,"
which
looks like an Allen wrench --
a single bent
piece of metal with a screwdriver
tip on
the end and the shank for a handle
that serves
also as a crank). |
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