510 METALLURGY OF CAST IRON.
rough is one and one-eighth inches in diam., or, in fine figures, 1.1284 inches, is all that is required. (Plans for casting plain bars are seen on pages 521 and 527.) It is well to have the lower end of this pattern made a little pointed for about three-fourths of an inch of its length, so as not to give a flat sand surface for iron to drop on, as in the case where the bar is entirely square on the end. In making this strictly plain, straight, round bar, the " cope " need not be lifted off, as the pattern can be pulled out endwise and the flask immediately np-ended, ready for casting (as seen on page 507), in less time than it takes to tell it.
Some might think a pattern rammed up on end in a wooden box (see page 527) would answer just as well. To do this and not have any swells on the bar requires considerable care in ramming the mould. By the plan here presented, no more time is required, and there is more assurance of unskilled labor obtaining a perfect, even, true round bar, free of all swells for its entire length, and -without a joint mark on it. These are essential requirements for a test bar.
Should it be desired to cast only plain bars, without the attached fluidity-strips, the hole in the end of the flask, as at N, Fig. 121, could be placed in the center of the flask instead of where it is shown in the figure.
Fig. 112, page 503, gives all the dimensions of^the single test bar flask shown in Figs. 117 and 118. Fi<>\ 113 shows a single bar with its fluidity-strip VS, as taken from a mould. The two projections shown on the bar in this figure, also at A and M, Fig. 103, page 482, constitute plans to be utilized to measure the contraction of such bars when they are moulded in jointed flask.
The simultaneous casting of duplicate test bars, illus- liquid iron. The lining used for the cupola is simply a coating ofnovice desires to use the smallest cupola practical for melting small samples. "............ " " i in square hnrH........................