That depends entirely on the magnet. I have quite a collection of small neodymium magnets, and they are quite strong (and useful). I don't believe eve the smallest of mine would fail to stick over 1/4 inch of bondo atop steel. If there's a literal hole, patched over, that's obviously a different outcome.GregDumond wrote:I like the idea of a simple magnet...if it sticks no bondo!
Jim mentioned a "rather weak" magnet. If you verified a particular magnet sticks not too strongly to primer/paint over metal, but is too weak to stick to anything much thicker, and practiced getting the "feel" on a car finish of known composition, one might become adept at judging thickness.
One more point: A magnet could easily chip paint if it's fairly strong, and you don't maintain 100% control of it. You'd want to put soft material over it to protect paint, but then that will change the "stick" you feel. A good purpose-built gauge sounds better and better, doesn't it? 8)
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