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Full text of "Metallurgy Of Cast Iron"

406
MKTAU.t'KCY   oi-1   CAST   IRON.
in the latter, is a section of a loeoniotive pump casting-made some years a^'<> in Cleveland, Ohio, and causing such trouble that it went the rounds of several foundries before «^ood castings were obtained. A section of this casting is seen in Fi^f. Si. It will seem strange to many unfamiliar with founding that moulders did not uncler-
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stand how to make such castings sound, but if any such ever come to have experience with foundries and moulders, they will find that too many of them are ignorant of the prineiples underlying UK* art of founding. The difficulty with the pump casting lay in there bein# cavities found at about H, as marked in \fig. Hi, when the section was bored out to form a valve seat. These pumps were cast on end and at all angles; many were made with g'ood lar^e skimming* ^'ak*s to hold back the dirt, thinking such to be the cause of the imperfection found. Besides this, they went so far as to make them in dry sand, but all of no avail. Finally or where we may expect the shrink holes? Such holes will always be found in the upper cast part of uniform solid castings, as seen at E in sample No. 18, Fig. 80, and in the body of heavy sections having light ones joining them, as at F, sample No. 19; that is, if in both cases such bodies are not fed with additional metal to feed the shrinkage. Where light parts join heavy oness to insure equal action in recording* tin* expansion and contraction at. each end of the bar. At f> is a recess, which gives guide to mala,1 the same in the mould, so that in pouring the bars lt open-sand," the metal will ** flow off" at this point when it comes tt> that level, and thereby insure all burs being1 east eioselv to the same thickness.of          ^