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Full text of "Modern Mechanical Engineering Vol-I"

Foundry Work

Introductory
The Work of the Foundries: What it Embraces.—Since the major
portion of this work deals with the products of the iron foundries, these
must receive the principal attention in this article. And it must be remem-                             ]|
bered that the essential methods of the iron moulder are also those of the
steel, brass, and malleable cast-iron foundries. The details in which these
differ from one another are so important that each engages the services of
its own specially trained craftsmen, who would have much to unlearn, and
learn, if they should attempt to take service in one of the shops of another
group. But what all have in common are the fundamental facts: that
liquid metal is poured into a matrix of sand, usually prepared from a pattern;
that the moulds are all subject to the same laws that control liquid pressure
and the shrinkages of metal; that the various methods of making moulds,
with one or two slight exceptions, are employed in all foundries alike.
Metal Moulds.—While the castings poured into sand moulds include                             [
probably 90 per cent of the total quantity of castings made, inuch the larger
portion of these being of iron, there is another and a steadily growing
group, the moulds for which are of cast iron or steel. It embraces the
chilled castings, and the more recently introduced permanent moulds for
pipes, and the extensive practice of die-casting, employed for small, more
or less intricate articles made in the softer alloys, and required in very large
quantities.
Subdivision of Tasks.—In the very extensive group of iron foundries,
there is much subdivision of tasks. This occurs in all the large shops, and
in many of those of small size. The product and the men are specialized.
The great subdivisions are: moulding in green sand, dry sand, loam; .core
making and machine moulding, each often classified under light and heavy.
In the machine department, further economies are effected. One man
makes bottoms only, another tops, while a third will core and close, ready
for a fourth to pour. A few years ago there were craftsmen to be found
in most shops who were competent to work in green sand or loam, in
light or heavy moulds, and at core making, while when occasional casts
in brass were wanted, an iron moulder would take on the task. These
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