Skeleton Core-iron
A core-iron consisting of wrought or cast iron rods cast in one or more plates or rings. It is the most efficient and convenient core-iron that can be made for any description of belt or jacket-core having metal on all its sides. Owing to their cage-like appearance, they are frequently termed cage-irons. See JACKET-CORES.
Skim-gate is any arrangement of runner that will arrest the skim or slag at some part intermediate to the pouring-basin and casting. If two castings are poured together in one flask, and one of the moulds filled by means of a fountain or horn runner connected with the bottom of that which receives the metal direct from the ladle, it is evident that all the dirt will remain in the latter, while the clean iron only will be forced into the former, thus making one casting a skin-gate to the other. Any intermediate receptacle, not necessarily a casting, may be thus employed to intercept the dirt; but by inserting a spherical object, as a ball, etc., for this purpose, and allowing the metal to enter it at a tangent to the circumference with force sufficient to impart a rapid rotary motion to the entering metal, the lighter scum is forced to the centre and there held until the casting or castings gated from the circumference of the ball are filled with clean metal. In order that this may be effective, the metal must enter the ball with force sufficient to keep it full, so that the castings may be fed from a point below where the dirt is held imprisoned. If a large quantity of metal must necessarily pass through a ball of limited size, a riser on the ball permits the accumulations to mount well above the ingates. See GATES; FOUNTAIN-RUNNER.