Ha, this thread came about two months too late for me! That Sheldon thing just f###ed with my s##t too!
I had a Campy Nuovo Record-era BB on my Vitus 979, along with some TopLine cranks, which fit nicely on it. Got a nice Ti BB that I found was ISO. No problem, right? Put it on and did not check how far spindle went in. Crank came loose mid-ride.
I switched to JIS and everything was fine. So I learned two things: TopLine/Grafton/Speed Stick cranks are JIS and so is old Campy.
The funny thing is, now just a few weeks ago a friend comes over with 105 cranks falling off his (French threaded) Vitus 979. Sure enough, they're bottomed out. This one seems cut-and-dried
JIS needs JIS situation. I make him buy a $12 JIS spindle and some bearing balls off Ebay to put in, but to get him going in the meantime, I find that the spindle in my collection that keeps the cranks farthest away from bottoming out is an old TA. And I have all sorts of Sugino and Specialized stuff in there too. Weird, right?
The machinist in me wants to agree with
Salamandrine. The variation must be fairly large. Considering with a 2-degree taper on each side, differences in width make wild changes in length, so this must make things tricky for manufacturing. Like a 0.1mm change in width results in a 1.4mm change in length, by my calculations, and the forging dies must wear out and make progressively larger spindles over the course of their service lives. And they've got to harden these spindles after all this, which can result in yet another dimensional change depending on the process. What a mess! I'm left thinking it's a wonder that any of the cheaper stuff fits anything else without being precision ground!