Fig. 81 shows the steps in the process of shaping a vessel from tin, brass, copper or. other sheet metal. The first step is to stamp out the disc, No. 1, from the flat sheet, called cutting or blanking. The shapes 2, 3 and 4 are then successively stamped between upper and lower dies which are counterparts of these shapes. This kind of shaping is known as drawing. Shape 5 is produced by spinning, and is done on a type of lathe shown in Fig. 82. A solid shaping roll of the contour of the work is held inside the shape as it revolves, and the spinning is done from the outside by pressure of a burnishing roll mounted on the lathe carriage.

Fig. 81. - Steps in Shaping Sheet Metal by Drawing and Spinning.

Fig. 82. - Spinning Lathe.

Fig. 83. - Steps in Pressing a Vehicle Hub from Steel Plate.

Any embossing or lettering raised from the surface of the metal is done by stamping.

Cylindrical metal boxes several inches long and less than half an inch in diameter, can readily be formed from discs of sheet metal by this process.

Another example of cold pressing is shown in Fig. 83. This shows the gradual changes of form in shaping a vehicle hub from a steel disc % inch thick and 15 inches in diameter. The flange of the finished hub is 7 1/2 inches in diameter. The steps are numbered consecutively. Annealing is necessary after about each third step, judged by the workmen for each piece.