The Dutch cO-shaped face is obtained by a die of the required section, and the curved slab, as it comes from the machine, slides over a mandrel which is lubricated by a current of water (Fig. 405), and is there cut into suitable lengths, while a fixed wire divides it into two parts, its breadth being double that of the tile.

Fig. 405. Cutting Machine for Curved Tiles (Schlickeysen).

By increasing the curvature of the die we obtain the shape of the semi-cylindrical Roman tiles. As they are conical, we place them, when they come from the mandrel cutter, on another conical mandrel shaped like the tile, and with an iron wire we take off the parts which project on each side (Fig. 370). The tile then is of the required shape (Fig. 405, to the left).

Another process, less economical, however, consists in expressing the paste in the shape of a half-cylinder bounded by a flat surface, thus having the appearance of a gas retort. An iron wire cuts off the flat part A B (Fig. 370), which is thrown under the machine, and the curved part is taken to a mandrel and shaped conically as above.

Particulars Of Tile Presses

The fitting ridge-tiles of the usual shape are made with screw or cam presses. As for those of complicated form or limited consumption, it is advisable, as matrices are very expensive, to make them by hand with plaster moulds of the desired shape, the moulds being constructed with the aid of models,