520 METALLURGY OF CAST IRON.
the flask as seen, then, by having a tapering projection cast on the bottom plates, as seen at X, Fig. 124, a few taps of a hammer on the binding strips F F are all that is necessary to secure the bottom plate in place.
Specifications often call for tests from turned bars. The author has arranged for such a test in a very simple manner, requiring but little machine work. At T, Fig. 127, page 522, is shown a bar having a swell cast on it. This can be made from six inches to eight inches long and of the diameter necessary to cause the "grade" of iron used to be readily machined to 1.128 inches, 1.596 inches or 1.955 inches diameter, so as to equal a one, two or three square inch area section and conform with the diameter of the rough bars given above for unfinished testing. The harder the grade of iron the larger diameter necessary at T to lessen the influence to chill or cause metal to be too hard for turning. But this should not exceed one and five-eighths inches diameter with the one and one-eighth inches diameter bar. Any iron that will be found too hard to be machined in this diameter of one and five-eighths inches of a swell, the second size or third size of a standard bar could then be utilized in having a swell cast on, half an inch larger in' diameter than plain rough bars called for. Whatever size of a swell is used, the same should be constantly used, in order to always have the same amount of stock to be turned off a test specimen. There are very few grades of iron which can not be machined from a body one and five-eighths inches diameter. The author has had bars with a swell of one and five-eighths inches diameter, cast on one and one-eighth inch bars with grades of iron used in mak- part ofstsld ask such, after having I''