Bulletin . is the fact that they allhave a considerable grinding action which abrades the metal facesand produces more pulverized material than where a simplecrushing action is employed. The jaw crushers also exert someabrading action, however, and no crusher having metal crushingfaces is devoid of the objection of producing material more or lesscontaminated with small particles of iron or steel. The operatorwho employs a crusher of either the jaw or gyratory type has todeal with the problem of cleaning his crushed material of iron andsteel particles. The simplest and surest method of accompli
Bulletin . is the fact that they allhave a considerable grinding action which abrades the metal facesand produces more pulverized material than where a simplecrushing action is employed. The jaw crushers also exert someabrading action, however, and no crusher having metal crushingfaces is devoid of the objection of producing material more or lesscontaminated with small particles of iron or steel. The operatorwho employs a crusher of either the jaw or gyratory type has todeal with the problem of cleaning his crushed material of iron andsteel particles. The simplest and surest method of accomplishingthis result is to screen out all the fine material, because the metal isinvariably ground off the plates in very small particles. The objec-tion to this method is the large amount of fine material wasted,which in some cases is as much as 10 per cent of the rock crushed. Apparatus to eliminate iron and steel particles from dry powderedrock have been only fairly successful and have not come into general. Figure 15.—Jaw crusher. use. The most successful method is to use a system of magnetsand to have the fine material in the form of a slime or slop. Theexpense of installing such an apparatus and of drying the cleanedslime will add somewhat to the average cost of crushing the feldsparbut will show a big saving as against the rejection of all the dust ma-terial from the crusher. Where the jaw or gyratory crusher has not been introduced theprimitive chaser mill is used for crushing the crude feldspar. THE BUHRSTONE CHASER. The buhrstone rolls are immense granitic wheels 5 to 6 feet indiameter and 12 to 18 inches in thickness. Two such wheels aremounted on a horizontal shaft and travel around a vertical shaft on 82 FELDSPARS OF NEW ENGLAND AND NORTH APPALACHIAN STATES. a bedplate of granite (fig. 16). This apparatus was for years theonly method of crushing feldspar and is to-day in many plants theonly apparatus employed for crushing the crude feldspar to a sizesuitable for grin
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou
