ROLL-TURNING.

SEC. 1. By the term roll, as used in the iron trade, is understood those cylindrical bodies which are made of castiron-sometimes of cast-steel, and also, though seldom, of wrought-iron. These cylinders are furnished with smooth turned continuations at each end, and are accurately placed and borne in a special frame or housing. A revolving motion is communicated to the rolls through a shaft coupled to their projecting ends, and this shaft may be driven by a steam engine, or any form of water-wheel, either directly or indirectly, by means of toothed wheels or belts. In each housing are placed at least two rolls, which is the most usual number, although the use of three together is becoming general, while under special circumstances four have been placed in the same housing. In the latter case, however, the rolls are arranged in pairs, and the common axis of one pair need be neither parallel to, nor in the same plane with, that of the other pair.

That part of the roll which is between the smooth turned continuations, and therefore lies free when in the housings, is the part which is used for rolling the iron, and is called the “body” of the roll. The smooth continuation, which revolves in a special journal, supported in the housing, is called the “neck," while the projecting ends upon which the couplings take their hold, are called the “pods.”

In the figure, a is the body of the roll; b b are the turned parts of the necks which rest in the journals or brasses, and

cc are the pods which project beyond the journals, and to which either a shaft or another roll is coupled. Every roll must have two necks. The notched part of the neck is unnecessary when no further coupling is wished, and when the upper roll is carried round merely by the friction occasioned by the passage of the iron, both notched ends may be dispensed with, but they are almost invariably added for convenience' sake, as it might be necessary to use the rolls coupled. Such rolls may be called "drag rolls," but differ from the coupled rolls merely in not being directly driven. The neck is not always cylindrical in its whole length, but is strengthened or curved outwards where it joins the body of the roll, as is shown in Figure 1. This is especially the case where the rolls must exert a great pressure on the piece to be rolled. The coupled ends are often notched or starshaped, as in the figure, but may also be made square, or of a circular section, with either two opposite or three equidistant notches, which are moderately deep.

For many purposes such as rolling plate or polishing hoop-iron-the body of the roll has the form of a smooth. cylinder. Such rolls are called plate or polishing rolls, and are exemplified in Fig. 1. In other cases, the body of the roll is made up of several cylinders, arranged like steps. Such rolls are called step rolls, and, in connection with peculiar guides, are used in rolling flat iron, spring steel, etc. In such cases they save many grooved rolls, which would be otherwise necessary. Figure 33, on Plate III., represents such a step roll, and Figure 34 shows the necessary guides; both figures are full size, and will be described hereafter.

§ 2. By the term "pass" is understood those sections of various forms which are produced by the relative position of the different grooves and projections which are turned upon the surface of the rolls; the form of the pass appears sharply marked on looking between the rolls when in position. The term groove is sometimes used as synonymous with pass; it is, however, preferable to confine it strictly to the groove on the body of a single roll. A pass may be formed by two cor

responding grooves, or by a single groove, into which there fits a fillet or ring on the other roll. It is best to call this ring the "former," in distinction to the term "collar," which has reference, as generally used, rather to the fillet, which, while dividing one pass from another, projects into a corresponding groove on the body of the other roll.

Just as two rolls are necessary for rolling, so two corresponding rolls are necessary to form a pass. It is, however, very seldom that a pass is formed by more than two rolls, for if three rolls are in the same housing (three high system), they lie horizontal, parallel, and with their axes in the same vertical plane, and the passes are formed by the middle, alternately with the top and bottom roll; therefore, by two rolls only. It is only in isolated cases, such as the rolling of thin iron tubes, that the pass is formed by four corresponding rolls which work together. Therefore, in all following descriptions, it must be always taken for granted that the pass discussed is formed by two corresponding rolls, unless the contrary is expressly stated. Now, one roll almost always lies vertically over the other, and in the same plane; therefore, in a two high train, where two rolls are used, they are called respectively the bottom roll and the top roll. In a three high train, however, when three rolls are placed above each other in the same housing, the third is called the midde roll.

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The passes formed by a pair of rolls are usually intended for successive use, i. e., one directly after the other; but other passes, or a set of passes, belonging to an entirely different series, may be turned on the same rolls, in which case the two sets are entirely independent of each other. tween two neighboring passes there must be left a proper space, which takes the form of a projecting rib or ring, and is therefore called a collar. The two corresponding rings at the end of each roll, which form the outside of the last pass, are also called collars. The term collar, in its proper sense, means a ring with rectangular edges. In order to distinguish those projections (other than formers, and not of rectangular form) which separate the individual grooves of

many varieties of rolls, it will be necessary to denominate them body-fillets and end-fillets respectively. The body-fillets, so called, are those which are on the body proper of the roll, and whose shape on either side is determined by the groove on that side, while the end-fillets are those which lie at the extreme ends of the roll, and which always have one rectangular edge, i. e., the outer one, though the inner edge may be of any form required by the adjacent groove. For the purposes of these definitions it will be sufficient to consider as collars all rings whose edges are rectangular, or nearly so, while all those of which each side is obviously turned to form one side of a groove, must be called body-fillets.

§ 3. The various forms of passes may be referred to the following seven divisions, according to the position of the pass and the way in which it is formed by the rolls.

1. OPEN PASSES.-In this form, as shown in Fig. 2, part of

the pass is turned upon one roll, the other and corresponding part upon the other roll. The divisions between the passes are formed by a fillet, turned on each roll; therefore the pass (either the box pass a or the Gothic pass b) is seen to be divided between the top and bottom roll, horizontally and nearly in the middle, as are also the body-fillets, c, d, e, and c', d' and e'. The bodyfillets remain, as it were, as remnants of the original body of the roll into which the necessary grooves have been turned; when the pass is large, however, it is roughly formed in casting the roll. The body-fillets of the top roll sometimes touch those of the bottom roll when it is desirable to preserve the size, and especially the height of the pass unchanged; but, as a rule, more or less space is left between them (a small play is, for instance, observable in the drawing), whereby the