CONTACT WELDlACi IN WTKE ttPKlNU KELAYS 



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strengths are being obtaiiuxl. These vahies are shear strengths obtained 

 on a dial indicator type of gage, reading directly in pounds, when the 

 contact is sheared from the wre along the wire axis. A minimum test 

 requirement of ten pounds has been established. 



Part II — Automatic Percussion Welding of Single Wire Combs 



Percussion welding is not new. Early work goes back beyond the l)e- 

 ginning of the c(Mitury, but little application has been made of it and only 

 a meager amount of literatiu'e is a\'ailable. However, this method has a 

 real field of usefulness as the application described in this paper will 

 show. The original Vang process, wherein a capacitor charg(Hl to a high 

 potential, often several thousand volts, is discharged across the gap be- 

 tween parts as they approach each other under a propelling force, is a 

 good general description of the method used. The arc so produced heats 

 the abutting surfaces before they collide so that a very thin layer of 

 metal is brought to welding temperature. The propelling force, con- 

 tinuing to act, brings the parts together percussively and the weld is 

 made. Little metal is heated and little heat penetrates the adjoining 

 metal; therefore, the heat balance problem is greatly minimized and 

 different metals weld together with little trouble. There is, however, 

 the problem of protecting personnel from high voltage. Also, the two 

 surfaces being welded must be insulated electrically from each other. 

 This excludes the use of this process for joining the ends of the same piece 

 of metal as in making a ring. 



The project undertaken by Western Electric development engineers in 

 the case of the single wire combs was the development of a machine for 



6 8 10 12 14 16 18 20 22 



WELD STRENGTH IN POUNDS SHEAR 



Fig. 9 — Weld strength distribution. 



24 26 28 30 



