DEVELOPMENTS IN MANUFACTURE OF COPPER WIRE 193 



same time, two for each of the first four pair of rolls and three on the 

 final rolls. At this period in the cycle of operation 800 H.P. is required. 

 When the rod mill was started eighteen passes were in use by several 

 of the most modern mills. A sixteen pass arrangement was adopted 

 for the new mill, in which the metal was subjected to a greater amount 

 of working in the earlier passes when it was hot. Later, as a result of 

 further study, fourteen passes were adopted. Fig. 6 illustrates graphi- 



1 7 5 9 io n \2 15 14 15 16 17 i8 

 18 Pass Mill 



§ 60 



i ^° 



l 30 



S 20 



K 10 



5 6 



7 8 9 10 II 

 16 Pass Mill 



12 13 H 15 16 



Fig. 6 — Per cent reduction 



cally the per cent reduction effected at each of the above passes. The 

 reductions plotted as the abscissa are in terms of reduced area in cross- 

 section at each pass and the passes reading from left to right are plotted 

 as ordinates. 



It is obvious that careful planning must be done in changing the 

 number of passes in a mill in order not to exceed the safe working capac- 

 ity of the mill rolls and stands. Such calculations have been made 



