Just a couple of clarifications: 1. Denier isn't obsolete in the sense of incorrect or not adhering to a standard (like the X/0 system); it has just been superceded by tex in the commercial thread world. If everyone in our little world used denier, fly tiers would be still know what they're buying a thousand years from now. 2. UNI hasn't stopped using the X/0 system, particularly for their most popular threads, because it will take some time for tiers to become used to denier. However, they do make the denier of these threads widely known so that tiers can make legitimate comparisons. 3. I have no difficulty splitting unwaxed 6/0 UNI-Thread (not UNI-Nylon which is flat and thus simple to split in all sizes): however, 8/0 is a challenge I've yet to master. 4. Another nifty "thread" to split for larger flies is UNI Stretch. How to Choose & Use Fly-tying Thread discusses most of these points in detail.
Cheers, Paul http://www.galesendpress.com -- Paul Marriner Outdoor Writing & Photography. Owner: Gale's End Press. Member: OWAA & OWC. Author of Stillwater Fly Fishing: Tools & Tactics, How to Choose & Use Fly-tying Thread, Modern Atlantic Salmon Flies, Miramichi River Journal, Ausable River Journal, and Atlantic Salmon.
