Starting a cut and cutting with a cutting torch.
a. Cutting torch.
(l) The cutting torch (fig 14) is an apparatus for mixing oxygen and
acetylene in definite proportions, burning the mixture in preheating flames that
are allowed to impinge upon the work, and directing a jet of high-pressure oxygen
to sever the ferrous material along the line of cut. In appearance, the hand-
cutting torch is somewhat similar to a welding torch, but it differs in its
construction and method of control. It consists principally of a handle,
connecting tubes, and head. The handle is equipped, at the rear end, with oxygen
and acetylene hose connections. A needle valve in the acetylene inlet connection
controls the supply. The oxygen furnished to the preheating flames is regulated by
a preheat valve on the side of the handle. A high-pressure oxygen valve, operated
by a trigger or lever, controls the cutting oxygen.
(2) In some cutting torches, the preheating oxygen and acetylene do not mix
until they are in the cutting tip. Such torches have three gas tubes: one for
high-pressure oxygen (top), one for preheating oxygen (middle), and one for
acetylene (bottom). In other cutting torches, the preheating oxygen and acetylene
premix in the torch body in a common mixing chamber. Such torches have only two
gas tubes: one for high-pressure oxygen (top) and one for the mixture of gases