Rolled Glass
An inferior kind of plate-glass about one inch in thickness is now made for common purposes by first obtaining the requisite quantity of molten glass in a suitable dipper and then emptying it on a casting-table, on the edges of which are the thickness strips, on which the roller travels as it spreads the glass over the surface.
Rolls are cylindrical rollers of steel or cast iron, which when mounted in the housings so that they cannot recede from each other, and provided with suitable gearing for causing them to revolve, are employed for reducing metals to plates, rails, bars, etc. Steel is fast taking the place of cast iron for the manufacture of rolls.
Cast-iron rolls are made to present a hard steely surface by casting the plain body in a smooth cast-iron chill-mould, the ends of the casting being formed in the sand or loam as for soft rolls. Common soft rolls may be swept horizontally, as described in "The Iron Founder," p. 274; also vertically, as an ordinary loam-mould; or they may be moulded from patterns in either of the positions mentioned--the only difference being that the pattern for horizontal moulding must be equally divided lengthwise, whilst the one for vertical would consist of a separate upper and lower neck and body patterns, with drag, check, and cope parts to match. The latter represents the method to be employed for chilled rolls, excepting that instead of the body-pattern and check-part, the chill is here substituted, consisting of a smooth cast-iron mould of sufficient thickness to absorb the heat rapidly, and thus produce a hard steely surface by preventing any separation of the chemically combined carbon into graphite at that part.
Whatever mode of moulding is adopted, it is all important that the metal be introduced at the lower neck, away from any direct action on the chill; otherwise the chill may be irretrievably damaged, and, if the stream be caused to flow in a tangential direction, the molten mass within will be made to rotate rapidly, and thus collect all the lighter scum in the centre, which, as the mould is filled, mounts upward, to be finally ejected into the open riser above. See RISER.
Rolling-mill is where the balls from the puddling-furnace, after being operated upon by the squeezer, are, by means of successive passes through the various rolls, reduced in bulk, with a corresponding increase in length, until the desired bars or sheets are produced. See MALLEABLE IRON; TRAIN.