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BELL SYSTEM TECHNICAL JOURNAL 



as a reference test and is resorted to only when the Rockwell test 

 indicates the material to be close to the limiting values specified. 



Work has been completed, resulting in the preparation of improved 

 specifications for leaded brass, annealed brass, nickel silver and 

 phosphor bronze and a similar investigation of rod stock in all grades 

 of these metals is now under way. It is interesting to note in passing 



Fig. 12 — Rotary selector used in dial system. 



that in the course of our investigations we determined that the endur- 

 ance limit of non-ferrous metals is only half that established for ferrous 

 metals, averaging approximately }i of the ultimate strength.^ 



For one of the rotary selectors used in the panel dial system we 

 developed a leaded phosphor bronze sheet containing approximately 

 3 per cent of lead which proved very valuable in terms of increased 



6 "Fatigue Studies of Non-Ferrous Sheet Metals," J. R. Townsend and C. H. 

 Greenall, Proc. A. S. T. M., 1929. 



