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How to Use the Ashenhurst Formula

Sett Calculation Using Ashenhurst's Formula

Ashenhurst's Formula
S = ( T × R ) ÷ ( I + R )

S = Sett
T = Number of wraps in one inch
R = Number of warp ends in one repeat
I = Number of itimes the weft intersects with the centerline in that one repeat

In each diagram below, the black disks represent ends of warp yarns. You are looking at the fabric edge on. It is a shuttle's eye view. The white line is the path of one weft yarn as it goes above and below the warp yarns. The turquoise line (with arrowheads at each end) indicates one repeat distance. The dashed purple line is the centerline of the ends of the warp yarns

Plain Weave, end view

R = 2
I = 2
A little algebra then reduces the Ashenhurst formula to S = T ÷ 2.

2-2 Twill

R = 4
I = 2
The Ashenhurst formula then becomes S = (2/3) T