Understanding fly tying thread diameters – denier, aughts, resistance and lady’s tights

a lot of good info here and i’m all for this thready revolution. saying ‘aught’ when having to depict thread diameters makes me feel stupid and somewhat dirty. maybe it’s the shotgun-shell connotation or maybe because it sounds like it might be swedish, i don’t know but whatever it is, i don’t like it.
what i do like however is this informative article, here’s a preview.


By  Christopher Helm

“In the late 1930’s, the Chenille Company created the “aught”( 3/0,6/0, 8/0, etc.)

system to indicate the size of thread. This was based on a system where the

number or “aught” was the base point and as the thread became smaller additional

zeros were added indicating that the thread was finer. As an example, a thread

with six zeros ( 000000) translated to a 6/0 thread. As other thread distributors

were born after the early 1960’s, they followed the same system which was

assigning a standard that does not provide as accurate a measurement for the fly

tier as denier.

In 1988, Tom Schmucker of WAPSI Fly, Inc. in Mountain Home, Arkansas

introduced a nylon thread simply called 70 UTC and 140 UTC based on denier,

which is the method of measuring thread. This is the system that the garment

industry uses for thread to sew clothing. Denier is defined as the weight in grams

of 9000 meters of nylon, polyester, rayon thread, etc. There is a correlation

between denier and breaking strength of nylon and polyester thread, the smaller

the denier number the lower pound/ounce breaking strength of the thread.”

click the link above for the complete file. enjoy !

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