Metal: It’s Like It Grows On Trees
Often, when talking about milling a log, I talk about the potential for it to have metal in it. I take for granted that everyone knows what I am talking about, but I was reminded recently that it is not always the case. I mentioned in an earlier post that a log had metal in it, and a friend of mine didn’t know what I was talking about. He asked, “How does metal get in trees?” Well, I am here to tell you how – any way imaginable. You name it, if it is made of metal, it is probably in a tree somewhere.
You see, trees are magnets for pieces of metal. Young boys put them in trees for fun. They might be in the form of one small nail to hold a target or a series of large nails every 12″ to anchor tree house steps. Single trees in a fenced-in back yard are especially susceptible because they are sitting ducks and the focus of much attention. Even adults get in on the action with big hooks to hold hammocks, clothes lines, and bird feeders. Not to mention the trees close to the street that get nails from everyone’s signs.
The beauty of the nail is that there is usually more than one. I always say, “Why put in one nail, when you can put in twenty?” I have often thought that if I find one nail, I should just ditch the entire tree, but that is usually only on hot days, and when I am cutting low-grade logs. Otherwise, I suffer through it, dulling blades and cutting at a slower pace, while I check the log with a metal detector before each cut. On those same days, I often think about a new program that I will start for school-aged children called “Save The Lumber,” where I will teach the importance of hammer restraint.
The secret to the metal situation is that the trees grow over the metal. Nails that were driven 70 years ago are deep within a log, with no sign on the outside. Certain trees, like oaks especially, will show stains on the end of the logs from the metal reacting with the tannin in the wood, but that doesn’t tell you exactly where the metal is, just that there is metal close. So these things just sit in there, waiting to tear up the saw blade. They usually don’t ruin the blades we use on the portable mills, but they make them very dull and mess up the set (which is the amount the teeth are bent out to provide clearance for the blade). Larger pieces of metal can wreak havoc on bigger equipment though, and be very dangerous. In fact, putting large pieces of metal, like railroad spikes, in trees was a tactic used by activists to try to deter logs from being harvested. These days, all mills have metal detectors, so this is less of a problem at the mill.
I get most of my logs from an urban environment and know that the bottom log is prone to have metal in it (usually between 4′-5′ from the ground, where people can easily reach). For me, it is part of the deal and I work with it. There are, however, plenty of logs that are better not to cut, but I usually suffer through them anyway. I had one recently that prompted this post, and I have put up a photo of the carnage to drive home the point. It was a beautiful 14′ long super-straight elm log that would have produced wide and perfect boards, except for the nails, nails, and more nails. It also happened to be the one that bent up my mill, causing me to make a new part, which I decided to grind on, which created sparks, that, in turn, burned down my shop. That was a log that I should have never messed with!