604 



THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1953 



4 s^ 



0.1 



12 5 10 20 30 40 50 60 70 80 90 95 ?8 99 



PER CENT 0«= TERMINALS BELOW INDICATED STRIPPING FORCE 



Fig. 8 — Effect of wire plating on stripping force. 



99.9 



curves run higher than the curves for the harder nickel silver in Fig. 5. 

 Fig. 6 shows that the presence of tin plate on a 0.013" by 0.062" terminal 

 increased the minimum expected stripping force by more than 1,000 

 grams. Figure 8 shows that on a 0.031" y 0.062" terminal that while the 

 effect of the tin plate on the wire was to raise the stripping force as 

 before, the increase was not as great as that in Fig. 7. It is also clear 

 that the thicker terminal of Fig. 8 results in a higher stripping force 

 than that for the corresponding thinner terminal of Fig. 7. 



In analyzing the effect of tool variations it has been convenient to 

 take a series of curves like those in Figs. 5 to 8, and from each curve 

 select two points, namely one for the average stripping force and one 

 for the average minus 3o- where o- is the standard deviation of the ob- 

 served values of stripping force. Using these two points for each of 

 several sets of curves a plot may be obtained of the average and minimum 

 expected stripping force as one or another of the parameters of the tool 

 design are changed. In this manner curves of the type shown on Fig. 9 

 were obtained. By preparing curves of this type for any given appli- 

 cation, the permissible range, Z, of variation of tool radius, /^, can be 

 obtained. This range includes those values of R which are above that 

 value which results in wire breakage and below that for which the mini- 

 mum expected stripping force falls below the stripping force limit. 



Table II summarizes the results of many of the tests which have been 

 run on a large number of samples in which the materials and dimensions 

 of the terminals, wires, tightness of wrap, etc., were varied. All of sample 



