Canadian foundryman (1921) . irty times its bulk of sandif properly baked. The temperature atwhich the oven should be kept dependson what kind of binder is being binder with a rosin base simply re-quires to be heated, and if heated at ahigh tempei-ature it will be destroyed, whereas the black compounds require tobe baked at a high temperature. Thesecret in using dry binders of any kindis to heat them to a high enough tem-perature to melt the binder. Many usersof black compound condemn it becausethe cores are too fragile, and are aptto break when being put into the on top of thi
Canadian foundryman (1921) . irty times its bulk of sandif properly baked. The temperature atwhich the oven should be kept dependson what kind of binder is being binder with a rosin base simply re-quires to be heated, and if heated at ahigh tempei-ature it will be destroyed, whereas the black compounds require tobe baked at a high temperature. Thesecret in using dry binders of any kindis to heat them to a high enough tem-perature to melt the binder. Many usersof black compound condemn it becausethe cores are too fragile, and are aptto break when being put into the on top of this, they are as hard asstone when the time comes to rap themout of the casting. This is not the faultof the binder but of the oven manGood ordinary cores can be made fromthe refuse sand of the gangway and oldburned cores mixed with black compound and tempered with water, if theyare baked in a hot enough oven. Everyoven should have a thermometer in con-nection with it and cores mixed withblack binder should be heated to a tern. FIG. 2—HOW IT WOULD APPEAR IF MIXEIWITH MOLDING SAND. pei-ature of 450 deg. Fahr. and main-tained at that temperature until thecores are baked to the centre. By thi:means the binder is melted and whiliin that condition it runs through th«pores in the sand and covers each grainbinding them together, and in doing s<it leaves open spaces where it had beeibefore becoming melted. These mak<vents similar to those left between th<grains in the silica sand cores. Th<quality of the sand is of minor importance because it is covered with thbinder, which is very hard when bakedBy baking the cores thoroughly thecan be handled with safety and wheisubjected to the heat of the melted metathe binder will be burned out instead 6being baked harder as is too often thcase. For first-class cores of this kin<a good mixture would be ten parts sharjsand, ten parts new molding sand, teiparts old cores and one part black compound. Another binder is known aliquid co
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectfoundri, bookyear1921
