Re: needing to haul together on a rope to remove a ferrous tool
Really? I've not seen a ferrous key in a long time! (not saying I disbelieve you, just that IME they're rare these days)
I have a ferrous key ring, but I don't think any of my keys are. House keys are aluminium, garage and padlock keys are something that is supposed to be brass, the bike and car keys are... [goes off hunting a magnet] - not sure what they are but not magnetic so most likely non-ferrous (unless there's a tiny amount)
[wanders off in hunt of more keys]..Ancient house key - aluminium. Pushbike pretend-lock key - oh, here's a surprise. This one actually IS ferrous.. I am quite surprised at that! Was a cheap crappy lock and I'm surprised they used something as expensive as plated steel!
Some sciencey/engineering stuff... When stuff is plated, the plating solutions can gain an amount of iron that can be transferred to the item. I had an argument with a guy where I was telling him that both zinc and copper were not magnetic, and he demonstrated some headscratchyness on my part by holding up a zinc-plated copper rod with a magnet. very simple and effective way to prove your point! But after talking to the platers, the guy showed me some markings on the hook that he said were "iron contamination", ie the zinc solution needed IIRC hydrogen peroxide (to precipitate out the iron) and filtering.
Point of the above is there may be small amounts of iron in a key that your normal household magnets won't notice but an MRI machine would have a field day with!
Biting the hand that feeds IT
