DIAMOND DIES FOR DRAWING OF COPPER WIRE 



33 



orientation of the drilled hole was determined by means of a back reflection 

 Laue photograph. 



Diamond stones which meet our drawing die requirements are mostly 

 octahedral in shape, a common crystal form of this material. These are 

 usually alluvial in character and predominantly of Brazilian origin with the 

 exception of a few Southwest African stones. 



9 CARBON ATOMS 



— i^^^— DIRECTION NORMAL TO 100 PLANE (CUBE EDGE) 



DIRECTION NORMAL TO 110 PLANE (FACE DIAGONAL) 



DIRECTION NORMAL TO III PLANE (BODY DIAGONAL) 



CLEAVAGE PLANE (ONE OF FOUR) 



Fig. 5 — Diamond structure and the directions of drawing hole axis to the crystallographic 



planes 



Our examinations of numerous die stones have shown that the positioning 

 of these is random with regard to a predetermined drilling axis. About 

 75% of those studied were drilled normal to the HI orientation. The axis 

 of the drawing hole in these cases was in the direction of a body diagonal 

 of the cube representing the crystal structure of the diamond. The HI 

 planes, the cleavage planes for the diamond, are those which appear most 



