DIAMOND DIES FOR DRAWING OF COPPER WIRE 21 



A large part of the success attained was due to specifications defining the die 

 requirements and the setting up of adequate inspection means to check the 

 new and recut dies for these requirements. Prior experience of this com- 

 pany and the cooperation of our suppliers greatly aided this policy. 



The following details of diamond wire drawing dies have been found to be 

 essential to the desired performance of these tools in ouf drawing operations: 



Shape and Quality of the Diamond Stone 



Stone Size 



Mounting 



Contour of the Die Hole 



Polish and Finish 



Pounds Pull to Draw the Wire through the Die 



Shape and Quality of Diamond Stones 



Round, clear stones of sound structure are selected, and these should be 

 free from cracks, pits, carbon spots, porosity or any flaws and imperfections 

 which would affect the present or recut drawing surfaces of the die. Round 

 is the trade term for stones of polyhedral sides, approximating a spherical 

 form as distinguished from flats and irregular, unsymmetrical shapes. 



Usually these stones are octahedral in habit with smooth rounded corners. 

 The coloration and clarity of the mounted stone should permit inspection of 

 all drawing surfaces, relief angle, approach angle and bell. A close-grained 

 stone as determined by the crystal growth lines seems best. 



Stone Size 



The size of stone for specified hole sizes, consistent with the quality of 

 stone previously noted, has been well standardized for the copper wire 

 industry by the American wire die manufacturers. Good die performance 

 has been obtained from these sizes. The average stone size of these manu- 

 facturers has been specified for our requirements. 



Mounting 



The mounting encasing the stone is a vital factor in the life of diamond 

 wire drawing dies. Diamonds when used for drawing dies ultimately fail 

 by breakage (i.e. cracks, spalling, chipping out) and not by erosion of the 

 wearing surfaces. Diamonds due to their formation and crystalline struc- 

 ture and to the physical properties resulting therefrom, are particularly 

 prone to breakage when subjected to fatigue, impact and disrupting tensile 

 stresses such as those commonly met in wire drawing operations. To com- 

 pensate for this weakness it is necessary to effectively encase the stone in a 

 mounting which adequately supports it on all sides. The methods of 

 mountings are many and varied. Mountings which are made by hot 



