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Full text of "Modern Mechanical Engineering Vol-I"

EXAMPLES OF  WORK

and corrected with the trying plane.   Each is glued to its fellow, a man
stationed at each end imparting a reciprocating movement to the lag about

Fig. 35.—Alternative Methods of Fitting Mouldings

Fig. 34.—Construction of a Lagged Pattern

half a dozen times to work out the surplus glue. Iron dogs driven in keep
the joint in contact until the glue has dried, and one screw is put in through
each lag into each cross-bar. The heads of these are sunk in to permit of
turning. When one half has
been prepared thus, it is
turned over, the other halves
of the cross-bars are set in
position by their dowels,
and the lags for that half are
fitted, glued, and screwed.
The halves are united with
centre plates, and the turn-
ing is done with hand-tools
or from a sliding rest. Done
by hand, the same method
is pursued, and time saved,

as in the turning of pipe patterns.   A steady is used to prevent sag about
the central portions.

Column Fittings.—All columns have flanges, with or without mould-
ings. These are nearly always prepared separately from the shaft, which is
necessary, both to keep the
thickness of the lags within
reasonable limits, and to
avoid short grain. Gene-
rally flanges, and frequently
mouldings, are fitted into
shallow grooves turned in
the shaft (fig. 35, top), and
with the grain running
transversely. They are
either glued-up in segments,
the better way, or cut solidly
and not recessed (fig. 35,
bottom). In some cases it is better to glue blocks on the lags, and to

Fig. 36.—Shows Print Continuous with Lags

turn the mouldings from these,
of these supplementary parts.

The choice depends on the proportions