DEVELOPMENTS IN MANUFACTURE OF COPPER WIRE 211 



In view of the difficulty of obtaining dies for drawing wire at high 

 speeds and the large investment in dies required for the proposed wire 

 mill, it was decided to undertake a laboratory investigation of the 



Land 



Fig. 21 — Diamond wire drawing die (outline sketch) 



manufacture of diamond dies suitable for drawing cable and magnet 

 wire. 



It was found that the dies suitable for high speed wire drawing re- 

 quired a differently shaped approach, a better polish, and a shorter 

 land ^ than used for low speed drawing. In addition, the origin of the 



Fig. 22 



stone, the shape of the diamond, and its setting are all very important 

 because of the internal strain to which the die is subjected during the 

 drawing operation. 



9 See Fig. 21. 



