Hurling chunks
And now, a question from the audience. Kate in Toronto wrote in to ask:
So, it’s 8am Wednesday and I’m trying to find out why the planer, in the shop I use, keeps taking 1 inch square chunks from the corner (face) of my perfectly jointed boards – when your site popped up…
It’s not snipe – it’s chunks. It happens on the ends of the boards BUT ONLY, it seems, when I get down to my final thickness and not before! It (the planer) is some kind of Italian job with disposable knives.
Thank you for your question, Kate! As someone who’s owned a planer for nearly four months and planed literally dozens of board-feet of lumber, I feel fully qualified to answer your question.
Here’s my theory.
As you probably know, lumber absorbs moisture more quickly at the ends. That’s why when you go to a sawyer, you see all their logs are painted at the ends. If they don’t paint them, they absorb moisture more quickly than the rest of the log, swell, and split. I’m theorizing that something similar is happening with your lumber, and the last few inches of each side are weakened, possibly from a recent moisture change.
Now, every time I joint or plane something, I’m prone to getting some small splinters flying out when I reach the end of the board. That’s because the blades are whacking into the wood and pushing backwards, and by the time you’re at the end of the board, you don’t have half a tree of lumber behind you to hold the whole thing in place. So instead of staying in place until the blade completes its cut and shears the bits off, they go flying rearword (don’t stand directly behind your planer when it’s running for this reason).
So my theory is that your wood is weakened, so instead of splinters of wood making their final departure into the great beyond of your floor, you’ve got whole chunks.
There’s another possibility–you’re a lucky bastard. That is, if you’re working with heavily figured wood, I’m jealous. But you’ll also be more prone to tearout. That’s because in figured wood the grain looks like misbehaving spaghetti; it actually undulates back and forth. When you cut a straight slice, you cut the grain in _two_ places (since it’s zigzagging back and forth), leaving it poorly secured. This leads to the common problem of tearout, common when you’re jointing or planing figured woods, where your gorgeous piece of curly lumber starts resembling a lunar landscape after a (very noisy) pass through the machine.
As to why it’s happening on the last pass? That’s got me stumped. Perhaps just a tribute to Mr. Murphy. Alternately, if the weak area is near the middle of the wood, then as it gets thinner on later passes it’s more prone to break bits free.
But for a solution, I recommend trying the following:
1) Tack a piece of scrap lumber securely to the back of the wood. If the first theory is right, this will be the “sacrificial” piece and will splinter instead of your valuable lumber. Make sure that the planer blades don’t hit whatever you use to tack it in place (e.g. finishing nails)!
2) Dull blades will cause/exacerbate both of these problems, since you’re whacking more and cutting less.
3) Ditto for taking a thick pass, although it sounds like you’re not.
Hope this helps!
–dan
(Your questions are welcome (danieljshapiro at hotmail dot com), as long as you don’t mind an incorrect answer)
(Yes, I asked her permission before I posted her mail)
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