Scientific Awevican. DECEMBER 18, 1807.| 393 … 6.—FORMING COUPLINGS. showed a small but con- acting steam hammer, stant superiority to shown in Fig. 7. The ends of wrought iron and steel tubing. They were made on wrought iron, the pressure being about one-tenth are then swaged down, the thread is tapped, and they three classes of wrought iron…
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