PATTERNS, CORES, FLASKS, AND MOLDS 441 



A core is the baked sand part of the mold and is made in 

 a separate device termed a core-box. The baked sand is 

 usually somewhat coarser than that of the mold, and con- 

 tains clay, flour, oil, sour 

 beer, or some other bind- 

 ing materials to prevent 

 it from falling apart when 



baked dry. A core-print ^ 

 is that part of the pattern 

 designed to make an im- 

 pression in the sand in FIG. 206. Cope and Drag of a Pattern, 

 which the core is held. 



A sprue is an opening in the cope, through which the metal 

 is poured. A gate is a channel cut from the sprue to the 

 impression of the pattern in the mold. 



509. Constructions of Patterns. Patterns may be built 

 up in two ways: (1) in a solid mass, as in the case of a small 

 cylinder pattern; and (2) in the form of segments, as in the 

 cse of the rim of n, pulley. All excepting very small patterns 

 are built up of several pieces of wood, even if it is possible 

 to find material large enough to make them in one piece, 

 because the shrinkage and checking of large timbers would 

 render the work valueless. Constructing the pattern with 

 small pieces of wood not only prevents warping and checking, 

 but also makes a much stronger article, provided the gluing 

 of the pieces is well done. This method of construction also 

 allows the rim to work more easily, because the direction 

 of working is always with the grain, and not partly on end 

 grain as would be the case with a solid piece of wood. 



In building up in segments, all pieces must be sawed with 

 the grain of wood and never across the grain, as cross-grain 



