This flier/bobbin assembly inserts ~18 twist per inch. There are 20 threads per inch on the flier axle at the left so you have some scale for the yarn. (Sorry the lines between the floor tiles confuse the pix. Look at where the single crosses from one band of yarn to the next.) This flier/bobbin assembly was designed to spin 40 hanks (of 560 yard) per pound -- 22,400 ypp. Traditionally that was a medium weight single. Prior to 1780, a spinning factory would have a whole room of spinners, spinning yarns of that weight. And they would likely have a whole rooms of spinners, spinning 60s (34,000 ypp). And they would have a whole room of spinners spinning "fines" -~ 40,000 ypp. In those days, every competent spinner could spin any of those grists at commercial speed. One thing that made that possible was the correct tools.
So when a spinner excoriates me, telling me that, "[I] am very wrong for thinking that [I] am the first to spin 30,000 ypp and that spinners in [her] region had been spinning that fine long before [I] started spinning.", she has it upside down. I know, that in the past, essentially every hand spinner could spin 40,000 ypp singles at a commercial rate, e.g., very fast. For example, in 1580, the Dutch were buying fine wool in Spain, having it spun and woven in Flanders, and selling the (fine) finished cloth back in Spain at a good profit. What I dislike is modern hand spinners pretending that it must be hard to spin 30,000 ypp singles. With the correct tools it is easy.
The flier is custom from Alden Amos. I had to design and make the whorl and bobbin. It is a reasonable grist, why can't I just buy a DD flier -bobbin assembly from Ashford set up out of the box to spin 22,000 ypp?
No market! Most of the modern recreational spinners that can spin that fine are very proud of their skill and experience that allows them to use lesser tools to spin such yarn. This gives them status in their circles, and they do not want some spinner that has only been spinning for a couple of years to use better tools and thereby spin as fine as what took them years and years to learn to spin. (Oh, and every time I accumulate 1/4" of yarn, the effective diameter of the bobbin changes and I have to wind off. At 20 k ypp, that is less than 100 yards, at 30 or 40 k ypp it is a lot more than 100 yards. At lower grists, this is a real problem.)
I learned to spin fine singles on the stock Ashford DD and lace fliers, so I know it can be done. At this point, I have spun fine singles on most of the modern mass produced spinning wheels including the CPW, and have a god idea of how much effort is required to spin fine singles on the different wheels. Many of those trials were conducted with cash in my pocket to buy a better wheel. However, spinning fine on modern wheels was so much work that I was willing to put a large effort in to finding a better way to spin such singles.
So, yesterday, I was in a roomful of very accomplished weavers ( many of whom are considered very good spinners) and I showed them that morning's work (after it had been washed, blocked, and rewound). They wanted to know what kind of fiber allowed me to spin that fine. (It is very generic Merino, that can be spun much, much fner.) They asked the wrong question. The right questions are, "What tools did you use to spin that fine? and "How long did it take you?" (365 yards in an easy morning of spinning.) With those tools, I can spin Romney, or Shetland, or Suffolk, that fine at almost the same rate.