The non-adjustable union nut wrench (fig. 1-29) is
used to assemble and disassemble launch valve piping
union nuts. These special open-end wrenches are
designed to pass over the piping and then slide onto the
union nut to fully engage five of the six flats, thus
reducing the probability of damaging the nuts.
These non-adjustable union nut wrenches
are the preferred type for launch valve piping.
Under no circumstances should any other type
of adjustable or open-end wrench be used on
launch valve piping fittings.
Box wrenches (fig. 1-30) 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
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 light-duty
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 corners of the nut.
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. A combination
box-open end wrench (fig. 1-31) comes in handy in a
situation of the type. You can use the box-end for
breaking nuts loose or for snuggling 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 1-31 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 wrenchDO 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 open.
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."
Figure 1-29.Nonadjustable union nut wrench.
Figure 1-30.12-point box-end wrench.
Figure 1-31.Offset combination wrench.