practical dia 0100 0100 0100 0095 0095 0095 0090 0090 0090of orifices in corrected 4 77 4 64 4 52 4 93 4 80 4 67 5 02 4 90 4 77 u03b4n u00d7 10 sup 3__________________________________________________________________________ from fig4 the 34 ideal orifice size 34 was then determined for each of the intermediate rows 2 thru 8 which would reduce the birefringence of the filaments of each row to 4 77 u00d7 10 3 it was further recognized that it is not feasible to have a different diameter for the orifices of each row of orifices on account of practical tolerance limitations accordingly the table 1 above also includes 34 practical orifice size 34 profile which consists of three differene orifice sizes across the spinnerette also shown in the table is the theoretical corrected birefringence profile when the practical orifice size distribution is used both the uncorrected and corrected birefringence profiles are shown in fig5 accordingly theoretically the birefringence cv could be reduced from 6 4 percent to 3 2 percent assuming no short term variability along the threadline due to transient conditions thereafter a 2 250 orifice spinnerette was modified according to the 34 practical orifice size 34 profile as shown in table 1 above a first trial was then performed with a graduated orifice size gos spinnerette in which the inside three rows of orifices had a diameter enlarged to 0 010 inches the middle three rows enlarged to 0 0095 inches and the outside three rows remained at 0 009 inches use of the spinnerette resulted in spun yarn with very good birefringence uniformity and very good elongation uniformity in general.