Figure 1-14.-Chain pipe wrench.
The strap wrench (fig. 1-15) is similar to the chain
pipe wrench but uses a heavy web strap in place of
the chain. This wrench is used for turning pipe or
cylinders where you do not want to mar the surface of
the work. To use this wrench, the webbed strap is
placed around the pipe and passed through the slot in
the metal body of the wrench. The strap is then
pulled up tight; and as the mechanic turns the wrench
in the desired direction, the webbed strap tightens
futher around the pipe. This gripping action causes
the pipe to turn.
Many special nuts are made with notches cut into
their outer edge. For these nuts a hook spanner (fig.
1-16) is required. This wrench has a curved arm with
a lug or hook on the end. This lug fits into one of the
notches of the nut, and the handle is turned to loosen
or tighten the nut. This spanner may be made for just
Figure 1-16.-General-purpose spanner wrenches.
one particular size of notched nut, or it may have a
hinged arm to adjust it to a range of sizes.
Another type of spanner is the pin spanner. Pin
spanners have a pin in place of a hook. This pin fits
into a hole in the outer part of the nut.
Face pin spanners are designed so that the pins fit
into holes in the face of the nut (fig. 1-16).
When you use a spanner wrench, you must make
sure the pins, lugs, or hooks make firm contact with
the nut while the turning force is transferred from the
wrench to the nut. If this is not done, damage will
result to tools or equipment or injury to personnel.
(ALLEN AND BRISTOL)
In some places it is desirable to use recessed
heads on setscrews and capscrews. One type of screw
(Allen) is used extensively on office machines and in
Figure 1-15.-Strap wrench.