916 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1954 



however, was not suited for use as the base metal of the contact block 

 because it was difficult to weld in the roll welding process used for fabri- 

 cation of the contact tape. A 70-30 per cent cupro-nickel was selected 

 for this base metal because it approximated the resistance of the pal- 

 ladium, a necessary condition for roil welding, and it did not have an 

 easily volatile component to weaken the percussion welds. 



Another subject investigated was the speed of approach of the parts 

 during the percussion welding operation. The comb and its array of 



SELECTIVE HITCH FEED 



TO DRAW TAPE FROM 



1 OF 3 REELS AND PUSH 



THROUGH DIES 



-."STEPPED ALONG" AS 

 CONTACTS ARE WELDED 



-0.040" DIA COMB WIRES 



Fig. 18 — Schematic of the percussion welder. 



