To find the diameter number (D) of a yarn
For firm yarns such as worsted wool and cotton
D = 0.9 x square root (yarn count x standard yards/lb)
For soft yarns such as woollen yarns and tweed yarns
D = 0.84 x square root (yarn count x standard yards/lb)
Ashenhurst's formula gives the maximum sett of a yarn. The formula
is based on:
number of ends of warp in one repeat of the pattern
number of times the weft passes from one side of the fabric to the other (intersections)
the thread diameter number (D)
Maximum sett = D x ends per repeat/(ends + intersections)
Few cloths would be woven to this standard of firmness which gives
the maximum sett possible for a square cloth (with the same epi & ppi)
and the same yarn for warp and weft. A good working sett is about 3/4
of this number or slightly more
An 8/2 cotton has 2 plies of size 8 yarn, with a final count of 4.
It has 3360yd/lb (840yd/lb x 4).
D = 0.9 x sq rt(4 x 840)
Maximum sett (plain weave)
= 52 x 2/(2+2)
Maximum sett (2/2 twill)
= 52 x 4/(4+2)
Last updated: February 24, 1999
Webmaster: Nancy M McKenna.