The sections are made of a great variety of dimensions. Iron merchants generally publish lists showing those that they keep in stock.
The sides a b, b c are sometimes equal, as in Fig. 117; sometimes unequal, as in Fig. 118.
These forms of iron are obtainable in lengths up to about 40 feet.
It will be seen that extras are charged for the smaller sized angle and T irons, also for sections exceeding 8 united inches, that is sections in which the sum of the length of the sides, or of the length of both and stem, is more than 8 inches.
Angle irons cannot well be rolled of a thickness less than 1/8f the width of one side. On the other hand, if they are very thick, there is a considerable percentage of loss of metal in the rivet holes.
They should have sides or flanges of equal thickness - holding up the full thickness to the ends of the flanges, not feather-edged.
Channel Iron, known also as half H iron, is a form frequently used in lattice girder bridges and similar structures.
The united inches in channel iron consist of the width added to twice the height.
This is one of the most useful sections of iron for fireproof and other floors, parts of bridges, roofs, etc., and is rolled in depths of from 3 to 20 inches.
An endless variety of sections is kept by different makers who generally publish full-size sections of their iron joists, showing the weight per foot run of each joist, and the distributed load that it will support.
Besides the above-mentioned there are a great many forms of wrought iron, some of which are in common use, others required only for special purposes.
A few of these will now be briefly mentioned. Their sections are shown below.
Bulb Beam (Fig. 126) is chiefly used for shipbuilding.
Bulb Tee Beam or Deck Beam (Fig. 12 7) is also used for ships, and sometimes for roofs.
Bulb Angle (Figs. 128, 129) also for ships.
Square Root (Fig. 130), used for riveted structures in which the feather edge would cause an empty space.
Double Angle or Z Sections (Fig. 131), used for riveted structures instead of a flat and two angle irons.