Bill Tindall, E.TN
>I am a frugal sort and have a question about this oil. What does it do that any light petroleum oil won't do, for example the oil used on brass instrument valves? Or WD 40, a mix of esters sort of like the vegetable oils?

In terms of composition, camellia oil is not much different than olive oil. The composition ranges of these two oils substantially overlap. Someone with a frugal streak, and an inclination to experiment, might do a comparison of the performance of these two vegetable oils.

Is it common to oil planes and such, and why? I don't and as long as my shop humidity stays below about 60% I have never had anything rust.

The thought of oil near wood does not seem like a good idea, though I suppose a very thin coat won't be a problem. I can see that a vegetable oil might likely be less a problem than a petroleum oil. Still, unless there is a compelling reason to oil woodworking tools, it would seem best to not do it.