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Full text of "Modern Mechanical Engineering Vol-I"

EXAMPLES OF  WORK

69

that can be moved along the body of the pipe and screwed in any required
position.   As this carries the print, a stopping-off piece is not wanted.

When turning long pipe patterns, the correct diameter is set in at each
end. A very light cut is taken about the centre,
not quite down to the finished size, because of the
spring and vibration present. The reduced section
is then embraced by a " steady " mounted on the
shears of the lathe bed, and a rough cut is taken
with the gouge from the centre to the ends. A flat
is then planed from end to end, checked with a
straight-edge, and rubbed with chalk or red lead.
This serves as a guide to turning down intermediate
sections, without the need of having frequent re-
course to the calipers and straight-edge to check
the progress of the work.

Bend Pipes.—These may be long pieces of
straight pipe with a bend at one end, or they may
be entirely curved. On the degree of curvature
depends the method of their preparation. " Quick
bends ", those of small radius (figs. 29 and 30), are
turned in halves on the face plate. Four quadrants being screwed to the
plate by their joint faces, and turned, provide two complete bends. Bends
of large radii are worked in halves by hand methods. From a rectangular
cross-section a polygonal shape is cut, leaving only minute angularities to

Fig. 29—Pattern for Bend Pipe
of Small Radius

Fig. 30

Illustrations of Pipe Bends

Fig.31

be removed, to produce the semicircular shape, which is checked with a
templet.
When bends are attached to straight lengths of pipe, abutting joints are
used (figs. 30 and 31), secured with dovetailed pieces let into the joint faces
and screwed. The same method is employed for uniting branch pipes at
right (fig. 32) or other angles, as for tee-pieces. Sometimes a plate of iron