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Full text of "Modern Mechanical Engineering Vol-I"

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' ii

made with a sweeped piece for the rim, rammed against outer and inner
curves, and having the arms formed with half cores jointed in their middle
plane. The halves are closed at A, the lower half core is open at B. The
projections seen are the sides of the grids. Bosses only have to be bedded
in bottom and cope.

Fig. 6 is a casting moulded without any pattern portion except a sweep
that forms a circular print, shown at A. Half a dozen cores (fig. 7) are made
in the box (fig. 8), which, when laid on a level bed, produce the holes for

the lever bars, and the
spaces adjacent for light-
ening. A central boss
has to be set in the
bottom and cope.

Cores,   bosses,   and
facing pieces often have

Fig. 6.—Casting of Capstan Head to receive the Bars
A indicates a circular print and the joints of cores.

Fig. 7.—Core for Capstan Head

to be set in by measurement. In some cases a templet is useful. An
example is given in fig. 9, used for making print impressions in the
bottom of the mould for a boilermaker's levelling block. The holes are
first pitched and bored correctly in the templet, then the print, having
a shoulder to determine the depth, is thrust into each hole in succession.
The half holes round the edges of the templet are laid against the cores
already inserted.
Moulding by Turning Over.—This method requires at least two
box parts, a top and a bottom, within which the mould is wholly contained,
and a middle part is frequently included. It is, of course, the ideal method,
because both faces of the pattern are treated exactly alike, each being
subjected to direct ramming of the sand against it. This is therefore the