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Category: Anglers All Travel

A Simple Guide to Understanding Fly Tying Threads

One of the most confusing aspects of fly tying can be thread selection. Sorting through a myriad of fly tying threads with varying labels can be intimidating.

We touched on this topic in a blog post a couple of years ago, so we thought it would be worth revisiting. Where should you start when choosing thread?

According to our shop manager and fly tying ninja, Greg Garcia, the first and most obvious consideration should be the color.

“Honestly, this is often more important to me than any other factor,” Greg said. “For example, if I like UTC orange for a particular fly more than Uni orange, that immediately narrows my choices. Danville olive isn’t the same as UTC olive. Start by finding the color you like for a particular fly.”

Once you’ve narrowed your color choices, it’s time to think about diameter and strength. This is where things get confusing. When considering diameter, it’s important to explain the difference between denier and the aught (X/0) labeling systems.

“Denier is a recognized term used across the textile industry, not just in fly fishing,” Greg explained. “However, the aught system is something invented by the fly fishing industry. It was introduced by Danville more than 50 years ago and provides little value in terms of a standard. That’s why you’ll see threads across manufacturers labeled as 3/0 but that translate to completely different deniers.”

The truth is, both of these labels fail to convey the critical properties of a thread for the purposes of fly tying. Diameter, breaking strength, flatness, twist, material and texture are all factors that you wouldn’t know by looking at a 6/0 or 70-denier label.

Here’s Greg’s advice; look for UTC 140, Danville 3/0 or Uni 6/0 when tying large flies. On small flies, consider UTC 70, Danville 8/0 or the Veevus 16/0.

“Don’t be afraid to experiment with different weights to see which you like best for a specific pattern,” Greg added. “In fact, in our Fly Tying 101 class, I have students using eight different varieties of thread in order to feel the differences in each.”

Finally, you may want to consider the flatness or twist of your desired thread. Most wound threads will bite into materials more effectively. While flat threads will provide a slimmer profile. Danville is an example of a wound thread, while UTC is more flat.

“Remember though, you can always spin your bobbin to open it up for a slim profile (counter clockwise for the right-handed tyer) or wind it tighter for tying in materials – that’s clockwise if you’re right-handed,” Greg said.

In conclusion, start by choosing a color, and then consider diameter, strength and twist in that order.

“The good thing is, there’s really no right or wrong when it comes to choosing thread,” Greg concluded. “You can use any thread in the world as long as you use proper tension.”

And that’s Greg’s closing tip for this discussion on threads – tension is critical!

“When working with any thread, you need to pull nearly to the point of breaking,” he emphasized. “Pull as tightly as you possibly can, and make sure you pull toward your chest as you tighten. Pulling downward will cause the materials to slip around. Pull toward you and be aware of tension at all times.”

If you need help with materials or any fly tying questions, please visit us at the shop in Littleton or give us a call at 303-794-1104. You can shop our online selection of threads here. Or you can check out the rest of our fly tying tools and materials here.

We offer free shipping on all fly tying orders over $10. And if you see it in stock on the website, that means it’s actually here in the store, so orders always ship quickly.