McKinley High School - President Yearbook (Buffalo, NY)

Page 41 text:

TUE flIi5.T1iS'AN 35 Andrew Maul SHRINKAGE Wlicii the casting is made of east iron, tbe Mg shrinkage rule is applicable. Slirinkage is caused tlirougli cbcniical action wbilc the inoltcn inctal in the mold is cooling, thereby the casting' is rendered smaller than the patterng an allowance innst therefore be inadc on all patterns to compensate for this contraction-the extent thereof depending on the kind of metal and the size of casting. Sbrinkage may be said to be an allowance on the dimensions of as pattern to inalce up for the contraction of the metal as it changes from a liquid to a solid. WVC were next given stock for the test bar. Aiter planing and Sf1lli11'l1lg the four sides and ends, we were told to put draft or taper on tbein. Draft is a slight taper, about Mg to the foot, on a patterng it facilitates its removal from the sand. FINISH May be described to be an allowance on certain surfaces of a, pattern so that the surfaces may be inachincd to their correct size. It is allowed only when designated on the drawing by the italic letter f.

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234: TUE A bf TISAN Julius Thursack Pattern Making A pz1t1ie1 11 defined a model for making the molds into which molten l1l0lf,Ell is poured To form a. casting. Pa,tte1'n making, then, is the art of COl.lSlTl'UClf- ing the model. for nlaking the mold in which the casting is formed. A pattern is usually made from a sketch, drawing or sample Casting, and must be cou- siiruetecl wi1'l1 due consideration to modern molding practice. Most patterns are made of white pine, 1T12ll10gEUly or birch. After our l,11l'1TOdl'lCl2lO11 to the bencll and Ina.el1i1:,1e tools amd the molding benell, we were given our first blueprint or Cl1'El,Wll'lg of a. test bar 1 x1 x12 . From the blueprint, we were required to make a full-sized layout on a board, and the use of the sl11'i11l:age rule was taught us in the 1uaki11,g of the lay-outg this rule is Mg to the foot longer than the standard rule.

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36 THE .':lRTISflN CENTER LINES We next learned about center lines and their importance to the joli and l'oundations from which to work or the starting place from which a layout is made. 1 The V block, frame and lever clearly illustrate the importance of the center line. . Up to this point, the patterns made by ns were easy to mold and only elementary principles in pattern making, as applied in the foundry, were taken upg they were for simple green sand molds. The next that was taken up was about patterns with green and dry sand cores, for cxampleg the washer, the link, the lever, faceplate and many others. The lever brings out items pertaining to irregular parting of the mold. The parted pattern. shows the need and use of the dowel. pins and the advantage of a parted pattern, over a solid pattern. We were also shown the balanced core, with core prints and core box. These prin- ciples were brought out in reducer, head T, T pipe, return-bend, and many others. The bracket is a good example of green and dry sand core work and it also illustrates the use of the tail core print. The large sleeve built up in segments, the curved armed hand Wheel, the llat and the armed illywheel brought out many other principles and processes. The coating or inish applied on patterns consists of two or three coats of shellac rubbed down smoothly. The foregoing is a brief outline of what We were taught on pattern making. 'We feel that we have covered and mastered the elementary principles of the art. The work and study were interesting and of practical value in addition to the training of the mind, eye, and hand.