The Moulder's and Founder's Pocket Guide (Paperback)

Book may have numerous typos, missing text, images, or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1851. Not illustrated. Excerpt: ... Mixed Sand Moulding.--Moulding in green sand with dried cores may be considered a mixed moulding, which requires particular knowledge of the composition and construction of cores. In previous pages we have spoken of core-sand, but we shall here treat upon the formation of cores, and the quality of the core-sand for particular purposes. The management of cores is a matter which requires some ingenuity; malformation often causes perplexing failures, and is in most cases the source of unsound castings. Cores are especially used in forming vacancies in castings, which cannot be successfully formed by the pattern. The forms of cores vary greatly, as may be expected; but in general, if made of open porous sand, free of vegetable and animal matter, and of coal, and if the sand does not contain too much clay, and the cores are properly dried, there is hardly any difficulty experienced on account of the cores. A caution not to be neglected is, that cores are never to be put into a green-sand mould until the very latest moment before casting. Cores which are not surrounded by metal on all sides, are made of stronger sand than others which are often not dried at all. In cores which are covered with metal on all sides, and have only one or two small vent-holes for the escape of the gases, as is the case with cores for narrow pipes, the sand is moderately mixed with free-sand. It is to have no more clay or adhesive matter than is just necessary to make it adhere for being moulded and dried. Sand of sharp grains, as pounded rock or slag, is more open than the composition of round grains, as river or sea-sand, and for this reason preferable. In many cases, yeast or meal water is used besides clay water to strengthen the core-sand, but these ought to be used cautiously, for not onl...