DIAMOND DIES FOR DRyiWliXC OF COI'I'FR WIRE 29 



oversize diameter limits consistent with best enlargement practice and over- 

 all operating efficiency have been set for each finisher and line die size. The 

 die sets are removed from the machine when any one die, with the exception 

 of the finisher, has reached the specified limit. Usually two finishers are 

 used for each set of 26 A.W.G. and one plus for the other final gauge sets 

 before returning these units to the Die Shop. This procedure has greatly 

 enhanced the economics of die costs, operating efficiency and wire quality. 

 It has also made possible the issuance of dies by the Die Shop for shop use 

 without the necessity for preliminary "tryout" in the drawing machines. 



Recutting Practice 



Diamond die recutting is a series of lapping operations in which the abra- 

 sive is diamond dust for obvious reasons and the lap or carrier is a suitable 

 pin or wire, usually steel, depending upon the specific operation. The 

 theory and practice of lapping tool gauges to a fine finish is applicable here. 

 The diamond dust imbeds in the lap, is held there temporarily stationary and 

 cuts the die stone when it is forced in contact with it. As its position is 

 fLxed relative to the lap, but moving with respect to the stone, it cuts the 

 die surface. However, due to the great hardness of diamond, appreciable 

 wear of the lap takes place and its shape is rapidly changed. In ripping 

 where the shaping of the die contour is done, the pin must be frequently 

 reground. It is necessary to have a hard material for the lap to keep the 

 diamond dust working in contact with the die surface and to retain its shape 

 for an appreciable time. Also, some diamond dust would imbed deeply in 

 a soft material and be removed in the grind. 



Successful recutting and reproduction of die characteristics require definite 

 procedures and controls. Specific hole size enlargement, surface require- 

 ments, frequency of lapping pin grinds, diamond dust additions, etc. are 

 essential for each operation to achieve the desired results. 



Standard commercial machines are used for the various enlarging and 

 refinishing operations. In general, recommended trade practices are 

 followed. 



Ripping (the roughing operation which removes the pressure rings, chips, 

 etc. and reshapes the die contour) is most important as it determines the 

 die contour and the subsequent degree of polish. We have found the RPM 

 of the drilling pin spindles to be a determining factor. Spindle RPM's 

 from 4,000 to 12,000 have been tried, and 5,000 RPM has been found to be 

 most satisfactory. Other important elements are the diamond dust size, 

 frequency of pin grinds, speed and kick of the reciprocating vertical motion. 

 A definite sequence of these factors is necessary to achieve the desired results. 

 A gradual breakdown of the diamond dust effecting a cutting and lapping 

 action as controlled by the centrifugal forces dispersing it in the liquid 



