Weave Repeat, Shafts & Ashenhurst Maximum Sett

Ashenhurst is a nineteenth-century rule of thumb that has survived because it is close enough and nothing simpler replaced it. Its yarn diameter comes from a constant of 28 over the square root of the English count, which assumes a round, uniformly packed cotton yarn at ordinary twist - so it is optimistic for a soft, low-twist or open-end yarn, which is flatter and packs differently, and it does not describe a filament yarn at all. Read the maximum sett as an upper bound for a comparable cotton cloth and not as a physical constant. The intersection count is fixed at two per repeat, which is right for a simple twill or a regular satin where each end rises once and falls once, and wrong for a weave with more than one float per repeat in the same direction, such as a rib, a hopsack or a broken twill; those need their intersections counted from the actual point paper. Shafts are given for a straight draft, which is the maximum a weave ever needs and often more than the minimum - a pointed, skip or grouped draft can weave the same structure on fewer, and any repeat sharing a factor with the twill step reduces further, which is why the count divides by the greatest common divisor here. A sett utilisation above about ninety-five percent is weavable but unforgiving: shed clarity falls, warp abrasion rises and the loom will find every weak end in the beam.