Fly Tying Thread Demystified, Part I.

fly tying bench

We all have our preferences, it seems. I tied with Nymo for years and years, but this thread disappeared from the supply chain back in the 1980s. Danville 6/0 Flymaster then became my preferred thread for at least two decades; then I moved on to Ultra thread for about five years, and have been on a Lagarun X-strong kick for the last two years.

As fly tyers, we display both innovation and complacency. Innovation in the fly patterns we explore and develop each year; and complacency in the threads and tools we keep on our fly bench, decade after decade.

I conducted a survey recently, not at all scientific mind you; but a survey none-the-less. I asked two-dozen or so of my fly tying friends about the threads they use. Are you selective? What is your favorite thread? Do you use different threads for trout and steelhead flies? What about colors? Can you describe what you like about this or that thread?

Here is what I learned. These people are all over the “thread-map”. A few first-rate fly tyers I know are still working through a lifetime supply of Nymo. A few started with Uni 6/0 and are still working with this thread decades later. Same goes with Danville 6/0 Flymaster Waxed Thread. A few are fixated on Ultra Thread; one on “any old 3/0 thread”; one on Petitjean Split Second Thread; a few on monocord; and two on Lagartun X-strong Thread. Oh yes, one tyer keeps a spool of Kevlar thread handy for his herculean tying exercises.

Each of these tyers demonstrates high quality fly crafting ability, each fishes their own flies, several tie commercially, but few were at all passionate about their fly tying thread choices. Only one, a commercial-scale tyer, talked much about the technical properties of threads. This led me to do a little digging about fly tying threads, and share what I learned. I soon realized that I had little real understanding about thread, a material that is as fundamental as a fly hook. Seems like I, too, was selecting my tying thread based largely on instinct and habit.

So I contacted my technical expert, Marcos Vergara, of Hareline Dubbin, and asked him to help me demystify fly tying threads. Thanks Marcos, for helping me understand some of the choices I have been making without even thinking. Here are some physical properties of fly tying threads that are important in that these qualities affect how the thread feels and performs in our hands.

Is the thread waxed? Some are and some are not. Some tyers prefer a waxed thread because it provides a little “tack” when they are applying dubbing, others either add a dubbing wax only where it is needed, and some tyers do all their dubbing without any wax.

Is the thread woven? Some threads are woven, some are slightly woven, and some are really almost entirely composed of a bundle of parallel fibers. A woven thread will be more on the “round” side; a non-woven thread will lay very flat on the hook.

Will the thread stretch? This characteristic is affected by two factors: the basic thread material and the extent to which the material is woven. Nylon threads stretch less than polyester threads; woven threads stretch less than non-woven threads.

Can we split the thread? By this I mean – can we carefully insert a needle in the thread and create a dubbing loop composed of the single strand of our tying thread? Woven threads are not suitable for splitting, period. Threads composed entirely of parallel fibers are easily split. Threads that are “slightly” woven may be split, to a reasonable extent.

How strong is the thread? By this I mean: how much tension can I apply to the thread before it breaks and I go screaming to the fridge for another brownie and milk to calm myself down. As fly tyers, we tend to be subjective in our assessment of thread strength. More experienced tyers can finesse the tension placed on their thread and be effective with relatively thinner threads that possess relatively lower break strength. Generally, Polyester threads are stronger than Nylon threads.

I’ll end Part I of this article on fly tying threads here. Part II will follow shortly and will get down to reporting the best sellers, colors, and evaluating the specific properties of Ultra Thread, Uni Thread, Danville Flymaster, and Lagartun X-strong.

Jay Nicholas

This entry was posted in Fly Fishing Gear Review, Fly Tying, Oregon Fly Fishing Tips. Bookmark the permalink.

2 Responses to Fly Tying Thread Demystified, Part I.

  1. two dogs says:

    Great article…………looking forward to the follow-on!!

  2. Dan says:

    I’ve always been a fan of Danville threads, especially 3/0 monocord. It’s strong, lays flat and just plain gets the jobs done. The only downfall is that it doesn’t come in a lot of colors.

    Here is a nice summary of the Denier system for measuring threads written by Chris Helm. It also lists most major thread brands with their denier rating.


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