Here's a thousand words at least:
http://bulgier.net/
All three brands pictured (SunTour, Campy and Shimano) are interchangeable, thread-wise. The Campag is 10 mm x 26 tpi, while the Japanese bolts are 10 x 1mm - in both cases, the same as their respective rear derailleur mounting bolts. 26 tpi is so close to 1.0 mm thread pitch as to be indistinguishable to me - either type bolt threaded into the other brand of perch by hand, no wrench needed. (As you know, Japanese derailleurs get threaded into Campy dropouts every day.)
The Campy is shorter as you can see, so if you used a Japanese bolt you'd need to use the Japanese 3-part expander thingy too. I think it might still thread a little too far into the Campy perch, possibly impinging on the lever itself, so it might need to be shortened a tad. But then it would be 100% impossible to tell you "cheated", once the part was assembled on the bike!
Simplex (not pictured), is a completely different design, with the bolt head on the near side not the far side, so they loosen counter-clockwise. I couldn't find my Hurets and don't remember their system.
Mark Bulgier
Seattle WA USA