Blading
FIG. 57
The blades are drawn from a rod consisting of a steel core coated with copper so intimately connected with the other metal that when the bar is drawn to the section required for the blading, the exterior coating drawn with the rest of the bar forms a covering of uniform thickness as shown in Fig. [57]. The bar after being drawn through the correct section is cut into suitable lengths punched as at A (Fig. [58]), near the top of the blade, and has a groove shown at B (Fig. [59]), near the root, stamped in its concave face, while the blade is being cut to length and punched. The blades are then set into grooves cut into the rotor drum or the concave surface of the casing, and spacing or packing pieces C (Fig. [59]) placed between them. These spacing pieces are of soft iron and of the form which is desired that the passage between the blades shall take. The groove made upon the inner face of the blade is sufficiently near to the root to be covered by this spacing piece. When the groove has been filled the soft-iron pieces are calked or spread so as to hold the blades firmly in place. A wire of comma section, as shown at A (Fig. [59]), is then strung through the punches near the outer ends of the blades and upset or turned over as shown at the right in Fig. [58]. This upsetting is done by a tool which shears the tail of the comma at the proper width between the blades. The bent-down portion on either side of the blade holds it rigidly in position and the portion retained within the width of the blade would retain the blade in its radial position should it become loosened or broken off at the root. This comma lashing, as it is called, takes up a small proportion only of the blade length or projection and makes a job which is surprisingly stiff and rigid, and yet which yields in case of serious disturbance rather than to maintain a contact which would result in its own fusing or the destruction of some more important member.
FIG. 58
