Design and Operation of New Copper Wire Drawing Plant: Part II - Equipping and Operating the New Wire Mill

By J. E. WILTRAKIS ALLOY AND D I A M O N D D I E S The experience gained in operating the older Hawthorne and Point Breeze wire mills demonstrated the importance of providing and maintaining dies of high quality. The hardest materials, alloys such as tungsten carbide and flawless diamonds, are used in these dies. The alloy dies are used in the No. 1 drawing machine where the wire surface and resulting die wear are relatively small per pound of wire produced. Diamond dies are used exclusively in the No. 2 machine. Definite problems were solved in maintaining dies to rigid specifications which include correct die contours, a finely polished surface, and definite die pull values. The cross section of a diamond die, Fig. 17, illustrates the general contour found to be most satisfactory for high speed wire drawing. The approach blends smoothly into the reduction angle where the wire is reduced in diameter one AW gage. The bearing is approximately 40% of the wire diameter. With the use of a contour projector, 100X enlargements of die impressions are periodically made to control the process. Well graded diamond dust is used to enlarge the hole in the die and for polishing operations. Dust graded by flotation methods, closely checked, offers the best results. For final polishing 6 micron diameter dust is used. A 30X wide angle binocular microscope is used to check the various stages of die making operations and of inspection as shown in Fig. 18. The following die pull requirements have been set up for each gage when reducing wire one AW gage size: AWG Size 15 16 17 18 19 20 Pounds Pull 75 60 49 40 32 25 AWG Size 21 22 23 24 25 26 Pounds Pull 21 17 13.5 11 9 7 After grouping dies of a certain diameter according to the pounds pull required, they are matched into sets for use in the No.