If you are going to put wood into your planer, or run it through your joiner, you should always make a quick pass with a hand-held metal detector first. It doesn't matter if the wood is salvaged from an old building or brand new from Home Depot; always scan it. Having any metal at all hit these blades completely ruins them. They are not that expensive to replace, but the adjustments can be pretty long and tedious to get good cuts again