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Full text of "Metallurgy Of Cast Iron"

< >r TKST   I-.AKS.            4 75
worthy of iiny serious consideration as a standard, that ••it ires us to take into account more than one-eighth v'h from the size of the test bar pattern used. The ,;:«mirnt \ve attempt to figure, up or down, to determine a metal's strength per square inch, or'the more we are (ilverted from the exact size, of the bar actually tested, the more \ve will, err in drawing correct comparative •Unctions in any *l tirade of iron. In order to • lain a relative knowledge of the strength of an iron .,c must coniine tesis to the use of one size of a bar (see pai^c 5^4), h*t that be a one-inch, two-inch, or three-isich square area bar, and its computation should only be permitted in taking into account any variations which may exist due to irregular work in the moulding and casting of any one of the three sizes that may be used. In testing bars, this effect from irregularity in moulding which can cause a variation in the size of test bars, made oil from the same pattern, should be taken note of in compiling any records of strength filed for reference or comparison. Note should be taken of the least variation which mii;hl exist in thesi/eof n standard test bar, as a few thousandths part of an inch in the diameter of a, bar is multiplied about three times in its circumference. A lit tit* variation in the si/,c of a test bar can make a bar considerably stronger or weaker, according as its diameter is decreased or increased from the size of the pattern from which the test bars are moulded. In compiling'this work, it will be observed thai the author has thought it correct to reco^ni/.e this factor, and hence lite adoption of the column, "Strength per square iiteh," .seen with some of the tables jn'iveil herewith. In order that the reader mav understand how anyiameter were not recognized, see pages 573, 577............^.15° <(