good grades of pig iron with a percentage of scrap. In a locomotive works where a large variation in the qualities of the different castings has to be made, the greatest skill on the part of the foundry foreman is required in selecting and grading his materials.
Moulding for General Castings. The various groups of castings require different methods of moulding. Many of the smaller pieces, of which a large quantity are required, are moulded by machine,- or “plate moulded.” In the latter case the patterns are of metal and cast or fixed on to a plate. If the shape of the article to be made allows of it, the whole pattern is placed on one side of the plate, but in many cases half the pattern is on one side, and the other half on the opposite side. The mould is then made in two portions, the second part being produced by turning the plate over. One of the main objects of plate moulding (apart from speed of output), is to save wooden patterns from being damaged by the constant knocking and shaking required to remove them from the sand. A large number of articles can be made from the metal patterns in plate moulding which are all of the same size without variation. Vacuum brake cylinders, which are very thin castings, are made in this way, and also many forms of smaller axleboxes, brake blocks, etc.
The large drag-box casting is made by “green sand” moulding on the floor of the foundry. The
