(119) The arc occupied by the flats in their traverse varies from 120 to 150 degrees, speaking roughly, so that in some way or other a flat course of that length, capable of adjustment, requires to be provided. By far the most common method of providing this is to fasten to the side of the machine at the upper edge of the frame =O= a flat plate, shown in Fig. 50, with its upper edge forming a segment of the circle required. This arrangement is the invention of the late Mr. Evan Leigh, and has been widely adopted. The shape of this plate, so far as its depth is concerned, is so arranged that it can be sprung or compressed into a smaller circle with the minimum amount of difficulty and strain. This is what is known as a “flexible” bend, and is in wider use than any other form. It is attached to the frame side by bolts, slots being formed in the bend casting at each end through which the bolts pass. It will be seen that the slots allow of a considerable range of movement in the bend, which is made use of in setting it after the wire has been ground. The setting is effected by springing the bend by means of screws, until a circle is formed equal to that required to enable the wire surface of the flats to be concentric with the wire surface of the cylinder. As a matter of fact, the setting is done by the carder by sound and by the use of a gauge, the combination of which permits him to ascertain fairly accurately that the flats are in a good working position. When the bend is set, it is locked against the frame by the bolts, and stops, which are placed midway between the points of support, are brought up to the under edge of the bend. The object of these is to uphold the bend, so as to avoid deflection from the weight of the flats. As the cylinder, which weighs 9 or 10 cwts., revolves always in one direction at a steady rate of 140 to 170 revolutions per minute, and as the pull of the driving strap is usually towards the front, it will be perceived that a tendency, at least, will always exist towards wear in the brasses at their front side. Thus it is possible that in addition to the necessity for providing for the lessened circle, it may be also requisite to take into account the movement of the centre in a horizontal direction. The latter difficulty, however, has been to a large extent overcome by the elongation of the bearings, which are now much longer in proportion to the diameter than was the case formerly. The special construction of the bearings in order to resist the action of wear or to afford means of setting will be treated at a later stage in this chapter.