UTILITY OF THE TEST BAR, ETC. 535
well as large numbers could, and make study an easy task to readily demonstrate their utility as being suitable for standard comparative tests.
The tests shown are all of solid bars cast on end, and they illustrate among other valuable features the fact that the two and three square inch area round bars record a greater strength per square inch than the one square inch area round bars. This series of tests also shows conclusively that 110 one should use a test bar smaller than of one square inch area with the expectation of making any fair comparisons of degrees in the strength, etc., of his irons.* While the one square inch area round bar shown does not record the high strength for strong metals that the larger bars do, it is made very evident that they do record degrees of strength fairly accurate for use in a comparative test for soft irons or those above 1.50 in silicon for ordinary testing, a fact also demonstrated by the specialty tests as seen in Table 96, page 466, showing a gradual rise, in denoting degrees of strength in different grades of iron ranging from 1,480 to 3,686 pounds per square inch.
The test bars shown in this chapter were cast during the month of May, 1896, and were kindly supplied by the foundries of the Lloyd-Booth Co., Youngstown, O., Philadelphia Roll & Machine Co., A. Whitney & Sons, both of Philadelphia, Pa., the Shenango Machine Co., and Graff Stove Foundry Co., both of Sharon, Pa. The test of " Bessemer," Table 113, was cast by the author.
Tables 108, no, x i r, 112, and 113 were tested by Prof. C. H. Benjamin at the Case School of Applied Science,
*This is in keeping with the recommendations of the A. P. A., not to use bars smaller than i% inches in diameter. (See next chapter.)ards, see pages 573, 577 and 571;.n page 573, which show that test bars should not be smaller than \y* inches in diameter, and cast on end, us such will tfive truer results than the [J4™inch round bar in general practice, especially in making comparison <>i; the widest ranges in grades.temper '' or damp- ,| |