Ah -- Bosworth spindles -- "Tornadoes in Wood" as their ad says!
The design of these spindles shows extensive study of spindle physics -- no surprise, since Jonathan Bosworth is an engineer!
You may be able to find either a Midi or a Mini Bosworth in a good "sock weight" (my favorite sock yarn singles spindle is 0.9 ounces / 25 grams, YMMV). Midis and Minis are their "middle" sizes, the Featherweights are lower-profile than the Minis, and the Maxis (aka Larges) are bigger than the Midis.
Given that, you have to get in to spindle physics a little bit -- if you have a Mini and a Midi at the same weight, how will they spin differently?
It's my understanding that the distance from the shaft of the outer edge of the whorl affects spin time -- so the Midi would spin longer than the Mini. But, closeness of weight to shaft means a faster spin -- so the Mini might spin faster than the Midi. Hmmm, I better go browse my personal collection for some "matching" Midis and Minis and test this out (grin!)
Has anyone tried this? Let me know!
If I've got the physics right, then I'd recommend a "heavy Mini" for tightly spun sock yarns, or a "light Midi" for not as tightly spun. Me, I like my sock yarn tightly spun :-)
(based on a question on spindlers, 10Apr2007)