die block that has holes for 3/16-, 1/4-, 5/16-, 3/8-,
7/16-, and 1/2-inch O.D. tubing, and a clamp to lock
the tube in the die block. It also has a yoke that slips
over the die block and has a compressor screw and a
cone that forms a 45-degree flare or a bell shape on
the end of the tube. The screw has a T-handle. A
double flaring tool has the additional feature of adapt-
ers that turn in the edge of the tube before a regular
45-degree double flare is made. It consists of a die
block with holes for 3/16-, 1/4-, 5/16-, 3/8-, and 1/2-
inch tubing, a yoke with a screw and a flaring cone,
plus five adapters for different size tubing, all carried
in a metal case.
CARE OF HAND TOOLS
Tools are expensive, vital equipment. When the
need for their use arises, common sense plus a little
preventive maintenance prolongs their usefulness.
The following precautions for the care of tools should
be observed:
1. Clean tools after each use. Oily, dirty, and
greasy tools are slippery and dangerous.
2. NEVER hammer with a wrench.
3. NEVER leave tools scattered about. When not
in use, stow them neatly on racks or in toolboxes.
4. Apply a light film of oil after cleaning to prevent
rust on tools.
5. Inventory tools after use to prevent loss.
TACKLE
A tackle is an assembly of blocks and ropes used to
gain a mechanical advantage in lifting or pulling. Figure
2-18 shows the name and location of various main parts
of a tackle.
In working with tackle, it helps you to understand
the meaning of a few simple terms you hear used. The
term fall means a rope, either manila or wire, reeved
through a pair of blocks to form a tackle. The hauling
part is the part of the fall leading from one of the blocks
upon which the power is exerted. The standing part is
the end of the fall of the blocks. The movable (or
running) block of a tackle is the block attached to the
object to be moved. The fixed (or standing) block is the
block attached to a fixed object or support. When a
tackle is being used, the movable block moves up and
down and the fixed block remains stationary.
The mechanical advantage of a tackle is the term
applied to the relationship between the load being lifted
and the power required to lift that load. Thus, if a load
Figure 2-18.—Parts of a tackle.
of 10 pounds requires 10 pounds of power to lift it, the
mechanical advantage is 1. However, if a load of 50
pounds requires only 10 pounds to lift it, then you have
a mechanical advantage of 5 to 1, or 5 units of weight
are lifted for each unit of power applied.
The easiest way to determine the mechanical advan-
tage of a tackle is by counting the number of parts of
the falls at the movable (or running) block. If there are
two parts, the mechanical advantage is two times the
power applied (less friction). A gun tackle, for instance,
has a mechanical advantage of 2. Thus, to lift a 200-
pound load with a gun tackle requires 100 pounds of
power, disregarding friction.
By inverting any tackle, a mechanical advantage of
1 is always gained because the number of parts at the
movable block is increased. By inverting a gun tackle
(fig. 2-19) a mechanical advantage of 3 is attained.
When a tackle is inverted, the direction of pull is diffi-
cult. This can be easily overcome by adding a snatch
block, which changes the direction of pull, but does not
increase the mechanical advantage.
2-12
