. The miller, millwright and millfurnisher. e greater the friction on the material the easier the feed ; the lesspressure required, the less power needed, and the greater the capacity for agiven fineness of grinding, with all the other conditions equal. The Stevens (round nib) rolls are nine inches in diameter for all less than eight inches in diameter seem unadapted to any of theoperations in milling. 390 DETAILS OF ROLLERS AXD FRAMES. Surface of Rolls.—The surface of the rolls may (i) be ground,ribbed or fluted ; or (2) it may have a roughish surface or grain ; or (3) itmay
. The miller, millwright and millfurnisher. e greater the friction on the material the easier the feed ; the lesspressure required, the less power needed, and the greater the capacity for agiven fineness of grinding, with all the other conditions equal. The Stevens (round nib) rolls are nine inches in diameter for all less than eight inches in diameter seem unadapted to any of theoperations in milling. 390 DETAILS OF ROLLERS AXD FRAMES. Surface of Rolls.—The surface of the rolls may (i) be ground,ribbed or fluted ; or (2) it may have a roughish surface or grain ; or (3) itmay be smooth and jiolished. If ribbed, these ribs may {a) be parallel totlie axis, or (/) they may have a spiral or twist given them. There may be(i) concave flutes in the convex cylindrical surface ; or (2) convex ribsraised upon the convex cylindrical surface ; or (3) they may partake of thenature of both these, and be waved or doubly rounded ; or (4) they mayhave the outline o£ the teeth of a wood rip-saw ; or (5) that of the teeth of a. Fig. 283.—Action of Smooth Rolls. cross-cut saw ; or they may have any one of a number of other sections ofrib, groove or flute, each having some special claims to our attention. Materials of Rolls.—Of the various materials used, chilled cast ironand porcelain biscuit are the most frequently employed ; the first either flutedor plain, and the second with a plain grain surface. Stone is apt to wearunevenly and too quickly. The influence of the material of the roll upon the pressure necessary toeffect a given reduction, is shown in tests made with middlings and othermaterials, with rolls of cast iron, porcelain biscuit, granite, etc. It was foundthat to produce the same amount of middlings flour with cast-iron rolls aswith porcelain, more than one-fourth more pressure was required. Dull CHARACTER OF ROLLS. 391 chilled-iron rolls work easier than smooth ones, although buyers seem todesire that new chilled rolls shall be polished. It is well
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectflourmi, bookyear1882
