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Fly Tying Thread, Denier, Ought Sizes, Thread Sizing and Breaking Strains

Monday, 6 October 2014  |  Admin

Thread diameters were created in the 1930s. In the fly tyers have been using 6/0, 8/0, 12/0  fly tying threads plus many others, however in 1988 WAPSI fly introduced a thread called 70 UTC and 140 UTC for their UTC threads based on Denier sizing. There has been confusion since!

Denier is defined as the weight in grammes of 9000 meters of polyester, nylon or rayon threads. There is also now for most threads a correlation between the breaking strain on most threads for examply typically a 70 denier thread will be stronger than a 30 denier thread. HOWEVER, GSP or Gel Spun Polyethylene is an exception to the rule as GSP can be from 3 to 9 times stronger than nylon or polyester of the same denier. For example Semperfli Nano Silk 30 Denier has a breaking strain of 1,140gm / 40 ounces yet the thicker Uni 17/0 or 40 denier thread made from nylon has a breaking strain of 140gm / 5oz, Nano Silk over 8 times stronger. This gets further confusing as even GSP's are not the same, for example Veevus 12/0 GSP breaks has a breaking strain of 530gm compared to Nano Silk 12/0's 1900 gm, 3.6 times stronger due to its special makeup! Presently, there are threads available, which although identical, are labeled with vastly different N/0 size

So the best we can hope for as fly tyers is a guide to the thread diameter so that we can guage the size of head that will be created using a thread.  Of course a twisted thread will be thicker than an untwisted thread which will lay flatter on the hook.

Thread Stretch

Nylon has about 25% stretch, polyester around 15% stretch, and gel spun only 3% stretch

Thread Aught Sizing Approx Denier
1/0 600D
3/0 180D
6/0 100D
8/0 70D
10/0 60D
12/0 50D
18/0 30D

Thread Twists

Most threads are made by twisting multiple plies to make the required size. Left Twist (or Z-Twist) thread is twisted to the left and works with almost all single-needle machines. Right Twist (or S-Twist) thread is twisted to the right and is used with some U.S. double-needle machines.

Approx Thread Breaking Strains vs Aught Sizes

Thread Material Approx Denier Aught Size Breaking Strain Lbs / Ounces Breaking Strain Grammes
Danville Nylon 70D 6/0 11oz 311gm
Uni Nylon 100D 6/0 1lb 13oz 822gm
UTC 140 Nylon 140D 6/0 2lb 12oz 1360gm
Semperfli Nano 6/0 GSP 100D 6/0 8lb 5oz 3,800gm
Wapsi GSP 100 GSP 100D   6lb 15oz 3,146gm
8/0 Threads   70D      
Roman Moser Powersilk GSP 55D 8/0 2lb 6oz 1,077gm
Benecchi Polyester 150D 8/0 1lb 13oz

822gm

UTC 70 Nyon 70D   13oz 368gm
12/0 Threads   50D      
Gordin Griffiths Sheer Polyester 72D 14/0 10oz 283gm
Semperfli Nano 12/0 GSP       1,900gm
Wapsi 50D GSP GSP 50D   2lb 5oz 1,048gm
18/0 Threads   30D      
Danville Spiderweb Mono 30D   5oz 140gm
Uni Nylon   17/0 5oz

140gm

Semperfli Nano 18/0 GSP 30D 18/0   1,140gm

 

Fly Tying Threads By Breaking Strain

 

Thread

Material

Approx Denier

Aught Size

Breaking Strain Lbs / Ounces

Breaking Strain Grammes

Danville Spiderweb

Mono

30D

 

5oz

140

Uni

Nylon

 

17/0

5oz

140

Gordin Griffiths Sheer

Polyester

72D

14/0

10oz

283

Danville

Nylon

70D

6/0

11oz

311

UTC 70

Nyon

70D

 

13oz

368

Uni

Nylon

100D

6/0

1lb 13oz

822

Benecchi

Polyester

150D

8/0

1lb 13oz

822

Wapsi 50D GSP

GSP

50D

 

2lb 5oz

1,048

Roman Moser Powersilk

GSP

55D

8/0

2lb 6oz

1,077

Semperfli Nano 18/0

GSP

30D

18/0

 

1,140

UTC 140

Nylon

140D

6/0

2lb 12oz

1360

Semperfli Nano 12/0

GSP

 

 

 

1,900

Wapsi GSP 100

GSP

100D

 

6lb 15oz

3,146

Semperfli Nano 6/0

GSP

100D

6/0

8lb 5oz

3,800

 

 
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