This
fit should not be so tight that it is necessary to force the work into
place, neither should it be loose enough to allow any considerable space
between the surfaces. The molten spelter will penetrate between surfaces
that water will flow between when the work and spelter have both been
brought to the proper heat. It is, of course, necessary that the two parts
have a sufficient number of points of contact so that they will remain in
the proper relative position.
The work is placed on the surface of the brazing table in such a position
that the flame from the torches will strike the parts to be heated, and
with the joint in such a position that the melted spelter will flow down
through it and fill every possible part of the space between the surfaces
under the action of gravity. That means that the edge of the joint must be
uppermost and the crack to be filled must not lie horizontal, but at the
greatest slant possible. Better than any degree of slant would be to have
the line of the joint vertical.
The work is braced up or clamped in the proper position before commencing
to braze, and it is best to place fire brick in such positions that it will
be impossible for cooling draughts of air to reach the heated metal should
the flame be removed temporarily during the process. In case there is a
large body of iron, steel or copper to be handled, it is often advisable to
place charcoal around the work, igniting this with the flame of the torch
before starting to braze so that the metal will be maintained at the
correct heat without depending entirely on the torch.
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