I had a huge oak tree on my property that I had rough cut and kiln dried. I planed it down today from 6/4 to 3/4 thickness and as I did it, the boards are showing a bend that they didn’t show when they were rough cut.
I’m building an entertainment center. I was going to glue up the boards into a 24×48 top, some shelves, and the face frame. I was hoping that as I cut the stock for the face frame, the bow would go away, but I was wrong. There is still a small bow in the 24″ rails/stiles. To give you some idea, I think the bow is about 3/8 over a 48″ length.
A few questions about how I can work with this:
-Why? …and how can I prevent it from happening as I mill the remaining boards.
-Am I screwed? Do I have a garage full of firewood now?
-For the top, if I were to alternate the boards and the direction of the bows, joint with biscuits, would the top be stable enough?
-Could I stack the material with a weight on it and (perhaps) eliminate the bow?
Thanks guys for the advice.
Edited 1/27/2007 10:22 pm ET by KenL
Replies
Ken,
How did you mill the wood you prepared? Did you first plane one face flat on the jointer and then use the face as a guide to get a square edge? Was your next step to use the flat face as a guide to start planing the 6/4 thickness down to the finished thickness? Did you reduce the boards to their finished thickness all on the same side, or did you take a little and then flip the boards, once you had two flat and parallel faces and take a little from each face as you were planing.? Sorry if this seems elementary, but I am just trying to understand your process.
How did you store the wood you received from the kiln, and for how long? In what environment? Heat? Humidity?
If you lay the wood that is already machined on a concrete floor, the top of the bow up, and apply some weight to the piece, it will straighten out enough for you to be able to work it, and you should not have too much difficulty. I would definitely do this before gluing up the top, and biscuits or splines are a good idea. Your idea of alternating the boards before glue up is a good idea. Check the end grain, and try to get a herringbone pattern. This will help keep the finished top flatter.
I am sure that you will have other opinions here shortly. I am interested to see them. I do not think you have a pile of firewood. Good luck. JL
Ken,
If you can, store the boards as they grew while part of the tree. i.e. as near vertical as possible, with the root end down. Store them that way for a couple weeks or even a month and they should stabalize to the point that most of the tension will be released from the wood unless they grew on the side of a hill or in the shade of a larger tree. If the bow/distortion doesn't improve by then, you might want to consider the fact that the boards will probably always have some internal stresses imbedded in them and they will change noticably with seasonal changes.
Good luck
JL- I used the jointer to get get a straight edge, then (for the boards that were narrow enough), I used the jointer to smooth one side. Because I was looking for 3/4" stock, I used the table saw to rip down to 7/8" thickness. That's when the bows became noticeable. I planed both sides, alternating every few passes, and depending on the roughness that needed to be taken down.I got the lumber last weekend from the kiln and it's been in my garage since. I think the humidity is a little high in there, but it's the driest place I have to store the wood. Also, it's all in 10ft lengths and the garage is only 9ft high, so I can't store it on end. I thought that because the lumber was rough cut, there was enough circulation between boards to keep them from getting moist.I certainly can bring the boards inside to stabilize for a few weeks. My bigger question is whether or not I should/could continue to mill the material as is, or let it all sit for another few weeks. I would have thought that coming out of the kiln and equalizing at the kiln would have been good enough.
Ken, when you sawed the boards to 7/8", you took more off one side than the other. This is what caused your problem. Always try to take equal amounts off both sides gradually, then sticker the stock so air can circulate around the boards evenly.Beat it to fit / Paint it to match
I spent the afternoon milling more of the stock with much the same results. Cut a slice of about 3/8" from the boards using incremental cuts on the table saw and as it cleared the blade, the boards showed the bow (concave towards the cut face).In retrospect, I should have had various thicknesses rough cut. It's all 6/4 and to mill it down to 3/4" will waste a bunch of wood. (now I need to figure out what to do with 100 bf of 1/4" thick stock, haha)I'll sticker and weigh it down my 7/8" thick boards for a week or so and see if that takes out some of the bow. Then run through the planer (both sides) and see if it gets any better.I'll experiment by cutting some of the boards directly in half (thickness) and see if the bow is any less.Any other suggestions? I'm all ears!
Ken
You have received a bunch of good advise. Lataxe gave you a good process for working with what you already have. Just be VERY careful when machining your wood (grooves and tongues and so on). Because the material is not going to be flat on the machine table, you will need to be sure that the cuts you are taking are consistent and are not shallower in some places than others. I am sure that you will be applying additional force as you pass the wood over the blade, so use a technique that will not mangle your hands in the process. Be VERY careful. As dangerous as working wood can be, it is even more dangerous when you are fighting the stock as you are machining. JL
Hi KenFor several years I've been making mouldings for picture frames (need to be very straight- only 1/32" deflection over 6') from black alder grown in waterlogged woods (I live in Lithuania- its very cheep - I use lots of it) Its very bendy, but excellent for hand carving. I have on occasions received entire lorry loads of this wood from the kilns totally unusable, this normally due to the wood being dryed too quickly or at to high a temperature. If this is the case with your wood I have found leaving the wood in a slightly damp location (garage) for 2-3 months removes most of the kiln . Also I have a reject pile ( in a slightly damp location) where moldings that are too bent for carving are thrown, after 6 months about 40% straiten of there own accord and seem to remain straight. As a last resort if the wood still bends after milling to size, wrap tightly several similar sized pieces together with plastic wrap (from packaging suppliers) and lay on a flat surface in the shop after a couple of months they should have straightened some.All the best
Ken,
Although perfectly straight and flat planks are the ideal, it is possible to safely use planks with bow in them. I have done so many times, as the nature of planks is to bow, for one reason or another. You simply need to orient them within the piece so that they pull each other straight when glued up.
One straightforward example with planks that have the small degree of bow you're talking about (but aren't also twisted, cupped or arc'd) is to glue them at right angles so that the straight edge of plank-A pulls straight the bowed side of plank-B; and vice versa.
Your "alternate bowed-plank panel" proposal will also work, in my experience, if the forces causing the bow in each plank are small and broadly similar (small differences in the degree of bow don't seem to matter).
Even when planks are unbowed, gravity will bow them when they are perched across a couple of cabinet sides or whatever. We don't worry about that bow as we know that the rectilinear construction and joinery of a piece will straighten everything up.
We are applying the same principle when we glue inherently bowed boards. The forces causing the bow just happen to be in the wood rather than due to gravity.
You can generally judge whether the bow and stiffness of a particular plank will be easily overcome by the joinery. There does come a point when the recalcitrance of the bow may induce a whole piece to warp slightly. Test each plank to see how much force is needed to push the bow out of it. If you can do it with the push of an average human triceps, when putting the plank bow-side up on a flat surface and letting gravity help, the rectilinear joinery is likely to keep all square.
Cupped, wound and arc-shaped planks are another matter of course. With these, you have to impose flatness.
Lataxe
Ken,
Is the wood stickered in your garage or just loose stacked? I would sticker it. It sounds as if it hasn't acclimatized in your shop yet. Do you have a moisture meter? If you do check it. Also, coming down from 1-1/2" to 3/4" in one shot could be part of the problem in wood that has been dried in a less than perfect way. If I read it correctly you took the bulk off of narrow strips on the tablesaw and planed down the rest. Maybe try to joint/plane part of the way, let sit, and final joint/plane later. Remember, equal amounts off each side. Wait a week or more between operations.
Was the kiln process up to snuff? Do they regularly dry hardwoods?
I hope some of this proves useful. Let us know how it turns out.
-Paul
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