Some common types of hand soldering irons are shown in figure 2-28. All high-quality soldering
irons operate in the temperature range of 500 to 600º
F. Even the 25-watt midget irons produce this
temperature. The important difference in iron sizes is not temperature, but thermal inertia. Thermal inertia
is the capacity of the iron to generate and maintain a satisfactory soldering temperature while giving up
heat to the joint to be soldered. Although it is not practical to solder large conductors with the 25-watt
iron, this iron is quite suitable for replacing a half-watt resistor in an electronic circuit or soldering a
miniature connector. One advantage of using a small iron for small work is that it is light and easy to
handle and has a small tip that is easily used in close places. Even though its temperature is high enough,
a midget iron does not have the thermal inertia to solder large conductors.
Figure 2-28.Types of hand soldering Irons.
A well-designed iron is self-regulating. The resistance of its element increases with rising
temperature. This limits the flow of current. Some common tip shapes of the soldering irons in use in the
Navy are shown in figure 2-29.