Brass tubing is more easily soldered, but not so good to
braze, and generally not so strong as copper, other things being equal.
Solid-drawn tubing is more expensive than welded tubing or an equivalent
amount of sheet metal, but is considerably stronger than the best riveted
tube.
Boiler ends may be purchased ready turned to size. Get stampings rather
than castings, as the first are more homogeneous, and therefore can be
somewhat lighter.
Flanging Boiler Ends.--To make a good job, a plate for an end should be
screwed to a circular block of hard wood (oak or boxwood), having an
outside diameter less than the inside diameter of the boiler barrel by
twice the thickness of the metal of the end, and a rounded-off edge. The
plate must be annealed by being heated to a dull red and dipped in cold
water. The process must be repeated should the hammering make the copper
stubborn.
Stays should be used liberally, and be screwed and nutted at the ends. As
the cutting of the screw thread reduces the effective diameter, the
strength of a stay is only that of the section at the bottom of the
threads.
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