oz, I've got a rather fat knife that I keep in my carry-on, along with a Leatherman tool, which also has a knife. The only times I've had problems is going through Narita. There, I have to pull out the knife, and they will measure the blade with a ruler. So far, its passed. Today, I cleared immigration between flights, and to my surprise, when I went back through the main security, they didn't say a word.

I note 'main security' above, because for a pure transit, the X-ray standards seem to be much more lax, along with the metal-detector screening, at most Asian airports. Only on initial entry to the system do I find that they are much more strict.