DEVELOPMENTS IN MANUFACTURE OF COPPER WIRE 207 



reductions. The five die arrangement is satisfactory according to the 

 results shown on the curve, but the heavy reduction at the first die 

 often results in rough or slivered wire. The six die arrangement, 

 therefore, gives the greatest factor of safety. The seven die arrange- 

 ment is less satisfactory since the elongation and tensile strength in the 

 finished wire are so close to the requirements. 



30^ 



1^ Lbs. 



25^ 



20^ 



10 Lbs. 

 15 



\afL 



5 Lbs. 



5% 



Lbs.O^ 



22 23 24 25 26 11 28 29 30 31 3Z 33 34 35 36 37 35 39 40 Die Size 

 1 2 3 4 5 6 7 6 3 10 II 12 13 14 )5 )6 Reduction 



Fig. 17 



The use of A.W.G. reductions for the finer sizes of cable and magnet 

 wire provides flexibility since a change in the size of wire can be ac- 

 complished simply by increasing or reducing the number of dies used. 

 Tests were conducted to determine the gain by using heavier reduc- 

 tions and annealing the wire before redrawing, and Fig. 17 shows the 

 increased reduction possible at the first die when the metal is plastic. 

 In this test, an annealed No. 22 gauge wire of 31 per cent elongation 



