A State secret? While gathering information to create a chart of the various bead sizes as well as their hole sizes, it seemed as if TOHO was the only manufacturer that did not publish the hole sizes for it's beads. Since various hole sizes for the same exact bead could be found on the internet, it was hard to determine which account was accurate.
Okay. So I go to the source.... TOHO in Japan. After explaining to the contact that while their ads boasted larger hole sizes, the exact measurements were still needed because we have so many varying sizes in threads/wire available to us and it's necessary to know how many passes you can make through a bead when you're designing projects.
According to the contact, the following information is true of their ROUND beads:
Round 11/0 can be used with Needle 0.6mm or below.
Round 8/0 can be used with Needle 0.8mm or below.
Round 15/0: Approx. 0.7 mm
Round 11/0: Approx. 0.8 mm
(Takumi Large Hole Round 11/0: Approx. 0.9 mm)
Round 8/0: Approx. 1.2 mm
Round 6/0: Approx. 1.5 mm
Round 3/0: Approx. 2 mm
3-Cut Large is equal to Round 8/0.
3-Cut is equal to Round 12/0.
3-Cut Small is equal to Round 15/0
I truly hope this information is helpful.