Spinning Fineness - Fact or Fiction?

WHAT IS SPINNING FINENESS?

The Spinning Fineness (SF) is a number which attempts to combine the Mean Fibre Diameter (MFD) and the Coefficient of Variation of Diameter (CVD) into a single measure of fineness to estimate the performance of wool when it is spun into yarn. SF is calculated from the following formula:

Where:

MFD = measured Mean Fibre Diameter (m m)

CVD = measured Coefficient of Variation of Fibre Diameter (%)

The equation has been derived so that the SF is the same as the MFD when the CVD is 24%. A value of 24% was chosen since this is a typical CVD value for a Merino wool sale lot or consignment.

The effect of CVD on the SF of a 20m m wool can be seen in the following table:

Mean Fibre Diameter (microns)	Coefficient of Variation (%)	Spinning Fineness (microns)
20.0	16.0	18.7
20.0	18.0	19.0
20.0	20.0	19.3	Spinning Fineness is Finer
20.0	22.0	19.6
20.0	24.0	20.0
20.0	26.0	20.4
20.0	28.0	20.8	Spinning Fineness is Coarser
20.0	30.0	21.2

What is the Effect of CVD on Processing Performance?

Rule of thumb: For a given MFD, a lower CVD will result in an improvement in processing (spinning) performance. A 5% decrease in CVD is equivalent to a 1m m decrease in MFD in its effect on spinning.

What Application Does Spinning Fineness Have to Fleece Measurement Results?

The SF formula was developed using a CVD of 24% (typical for Merino sale lots). For fleece measurement samples (midsides) a CVD of less than 20% is more typical. Placing emphasis on the SF of an individual animal can be misleading since it is likely that the SF will be lower than the measured MFD. The most important price determinant for wool is MFD, not SF. SF may have some use for the ranking of individual animals, but little research has yet been done in this area.

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