Figure 1-4.-Bonney wrenches.
Open-end wrenches may have their jaws parallel
to the handle or at angles anywhere up to 90 degrees.
The average angle is 15 degrees (fig. 1-3). This
angular displacement variation permits selection of a
wrench suited for places where there is room to make
only a part of a complete turn of a nut or bolt. If the
wrench is turned over after the first swing, it will fit
on the same flats and turn the nut farther. After two
swings on the wrench, the nut is turned far enough so
that a new set of flats are in position for the wrench,
as shown in figure 1-5.
Handles are usually straight, but may be curved.
Those with curved handles are called S-wrenches.
Other open-end wrenches may have offset handles.
This allows the head to reach nut or bolt heads that
are sunk below the surface.
Box wrenches (fig. 1-6) are safer than open-end
wrenches since there is less likelihood they will slip
off the work. They completely surround, or box, a
nut or bolt head.
The most frequently used box wrench has 12
points or notches arranged in a circle in the head and
can be used with a minimum swing angle of 30
degrees. Six- and eight-point wrenches are used for
heavy duty; twelve-point for medium, and sixteen for
One advantage of the 12-point construction is the
thin wall. It is more suitable for turning nuts that are
hard to get at with an open-end wrench. Another
advantage is that the wrench will operate between
obstructions where the space for handle swing is
limited. A very short swing of the handle will turn
the nut far enough to allow the wrench to be lifted
and the next set of points fitted to the comers of the
One disadvantage of the box-end wrench is the
time loss that occurs whenever a craftsman has to lift
the wrench off and place it back on the nut in another
position when there is insufficient clearance to spin
the wrench in a full circle.
After a tight nut is broken loose, it can be
unscrewed much more quickly with an open-end
wrench than with a box-wrench.
box-open end wrench (fig. 1-7) comes in handy in a
situation of the type. You can use the box-end for
breaking nuts loose or for snugging them down, and
the open-end for faster turning.
The box-end portion of the wrench can be
designed with an offset in the handle. Notice in
figure 1-7 how the 15-degree offset allows clearance
over nearby parts.
The correct use of open-end and box-end
wrenches can be summed up in a few simple rules,
most important of which is to be sure that the wrench
properly fits the nut or bolt head.
When you have to pull hard on the wrench, as in
loosening a tight nut, make sure the wrench is seated
squarely on the flats of the nut.
Pull on the wrench DO NOT PUSH. Pushing a
wrench is a good way to skin your knuckles if the
wrench slips or the nut breaks loose unexpectedly. If
it is impossible to pull the wrench and you must push,
do it with the palm of your hand and hold your palm
Only actual practice will tell you if you are using
the right amount of force on the wrench. The best
way to tighten a nut is to turn it until the wrench has
a firm, solid feel. This will turn the nut to proper
tightness without stripping the threads or twisting off
the bolt. This feel is developed by experience
alone. Practice until you have mastered the feel.
The socket wrench is
wrenches in the toolbox.
one of the most versatile
Basically, it consists of a