Canadian foundryman (1921) . APH. 36 Volume XII. Students Course in Foundry Practice—Sand Sharp Sand, Round Sand, Moulding Sand, Core Sand, HeavySand, With Spaces Filled With Moulding Sand—How Ram-ming Affects the Vent of the Sand. By F. H. BELL AS mentioned in our last lesson,sharp sand is the most desirableas a base for green molding sand,while sand with a grain as near roundas possible is to be preferred for coresand. In Figure 1 will be seen samplegrains of a good sharp sand. If agood average grade of molding sandis washed it will be found to containabout 85 per cent, of grains similarto t
Canadian foundryman (1921) . APH. 36 Volume XII. Students Course in Foundry Practice—Sand Sharp Sand, Round Sand, Moulding Sand, Core Sand, HeavySand, With Spaces Filled With Moulding Sand—How Ram-ming Affects the Vent of the Sand. By F. H. BELL AS mentioned in our last lesson,sharp sand is the most desirableas a base for green molding sand,while sand with a grain as near roundas possible is to be preferred for coresand. In Figure 1 will be seen samplegrains of a good sharp sand. If agood average grade of molding sandis washed it will be found to containabout 85 per cent, of grains similarto these, and about 10 per cent. balance will be made up of iron ox-ide, lime, magnesia, soda, potash, alkali,etc. The quality and quantity of theforeign matter which is associated withthe sand and clay go a long way in de-termining the grade of the molding much lime and iron is present it tendsto flux the sand and create a slag whichadheres to the casting and in fact actu-ally mixes with the melted iron and. FIG. 1- SAMPLE GRAINS OF GOOD SHARPSAND. forms part of the face of the pure silica and pure alumina aremixed in proper proportions they makea molding sand which will peel from thecasting, leaving a clean metal surface,but not having a fluxing material itbakes into a solid mass like pottery andhas to be sifted out before the sand heapcan be cut up for use again. It willtherefore be seen that while the foreignmaterial has its undesirable features, italso has its desirable ones, and that asand suitable for the work being donemust have the right proportion of eachingredient. To give a definite explana-tion of the proportions required it wouldbe necessary to go into chemistry, whichmight be unintelligible to a good manyfoundrymen, but without going deepinto the subject I would refer to themelting of metal in a brass foundry. Everyone who has had experience inthis line knows that metals which arehard to melt are easily melted whenmixed together. So it
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