Many times the jobbing foundry may find it expedient, where patterns and core boxes are furnished by the customer, to make certain changes which will reduce the cost of production; for, unhappily, the patterns furnished sometimes show a great desire on the part of the pattern-maker to produce the patterns cheaply, without making due allowance for difficulties encountered in the foundry.
The practice of substituting green-sand cores for dry sand has many possibilities. As an example, consider the case of a flange and spigot pipe 72 inches long and 6 inches inside diameter. The pattern furnished was satisfactory, as was the half-core.box, until it was found that the number to be made each day was gradually increasing and the number of half cores to be dried was seriously interfering with the production of the regular cores required. It was decided by the foundry management to adopt the use of a green-sand core, and not only relieve the core ovens, but also effect a considerable saving in core sand and core hinders. To make a green-sand core it was necessary to make the core box. The method used was as follows:
First, a half core was made in the original box, and when this was dried it was placed on a new mold board as shown in Fig. 82. Over this was placed lagging of the desired thickness for the casting, as shown in the figure; then over this were placed the loose pieces b to form the ends of the box and part of the hinge c, also forming a part of hinge on drag half of box, and e and g acting as strengthening ribs.
Fig. 85. Complele Core Placed on Hones.
With these loose pieces in position the drag was duly rammed and rolled over, the cope was rammed and the dry-sand core secured in and lifted off with the cope. The loose pieces were withdrawn from the drag, and the mold was properly finished; when closed and poured, this gave a satisfactory casting of the drag half of the core box. The cope half was made in the same way, the only change being in the shape of the loose pieces forming the ends as seen in Fig. 83.
An arbor being required to carry the green sand, it was made of cast iron, as shown in Fig. 84. To make the green-sand core, first riddle sand in the drag half of the core box; next place the arbor as shown in Fig. 83; then fill and carefully tuck the sand under the flanges on the arbor. The cope is simply filled with sand and rammed, and both drag and cope are struck off level with the joint. The two halves are now closed, as shown in Fig. 85, when the cope may be rolled back to its former position and the core removed from the drag half of the box by lifting an arbor extending through the end of the box.
The core should be placed on horses as shown in Fig. 86, so that it may be repaired if necessary and blackened. Fig. 87 shows the complete mold with green-sand core in position.
In this way a satisfactory core box was made without heavy expense for patterns, as the foundry carpenter or flask man was able to produce the loose pieces from a rough sketch furnished by the foundry foreman.