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Recently, I got a question from a customer regarding a crack forming in his solid wood countertop. He built the top out of flat sawn white oak lumber and he wanted to figure out what caused the crack and hopefully, how he could repair it. Luckily, the repair is simple (just some glue and clamps), but he really needed to address the cause of the problem or the countertop would most likely crack again.
When he sent me photos of the crack, he also sent me photos of the how he attached it to the cabinets, which was very helpful. The vintage metal cabinets have a bracket in each corner with a hole just large enough for a screw, but not large enough to allow for any movement in the top. In this case, the wood was stuck in place and had no choice but to split when it shrunk in width.
I recommended to simply make the holes in the metal bracket bigger and to add a washer or use a large-headed screw to allow the top to move side to side while still being held down. The secret is to tighten the screws just enough to hold the top in place, but loose enough to allow it to move if the wood starts to pull.
This particular solution was pretty simple, but only because I have seen it many times before, and I knew what caused it. Without understanding how wood moves, the diagnosis wouldn’t be so apparent. Even though most people don’t worry about wood movement as much as I do, I always try to get them to understand the most basic premise, which is that wood moves more in width than it does in length, and you need to allow for that movement.
In woodworking in general, this disparity in movement is referred to as a “cross-grain situation”, when two pieces of wood come together with grain perpendicular to each other, then they want to pull in opposite directions. It happens all of the time in furniture construction, and it must be addressed to avoid catastrophic failures. In the example above, the setup was the same as a cross grain situation because the metal cabinet will not change in any dimension, while the wood moves in width.
When attaching wood tops of any kind, whether it be a wood countertop to a cabinet or a table top to a table base, you need to allow the top to move or it can split. The good news is that there is more than one way to attach a top and still make allowances for this movement.
The first and most common way, as mentioned earlier, is to make an oversized or elongated hole and to make up any differences with a washer or large-headed screw. Assume that any problems will be caused by excessive shrinkage and make sure that your holes are big enough and that your screws are placed in the holes so that the top has room to shrink.
Another method, which I like to use on tables, is to make blocks to fit into dados on the insides of the aprons. They don’t take too long to make and can easily be added wherever necessary. The blocks should be made so that tightening up the screws will just pull the top snug, like a perfect fitting tongue and groove joint and placed with a little separation to make sure nothing binds. They work great, and I think they look great too.
When attaching a top with a propensity to move, understand that all of your attachment points don’t have to have play in them. For example, you can firmly attach a countertop to the front of a cabinet as long as you allow the top to move in the back. Or, on table tops, you might choose to firmly attached the top in the middle of the width and allow the outside edges to move. This is perfectly acceptable and keeps the top centered on the base.
The main point to remember through all of this is to allow the wood to move. You can only really cause a problem if you don’t allow it to move. And remember , if you find that it is moving too much for your liking you can always go back and firm things up once you understand the potential problems.
For a more thorough description of wood movement click on these two earlier posts Have Your Heard About Shrinkage? or Why Quartersawn Lumber is so Stable: The 0-1-2 Rule In Action, to read a link on the subject. I think it is probably the most important subject for any woodworker to fully understand.
I am a woodworker, and as a woodworker I live by a certain set of norms which dictate that I be accurate, but not ridiculously accurate. After all, wood changes size all of the time, so there is a limit to how accurate we can be and how much we should really worry about it. For most of us, a few measurements in a job are critical and the rest of the pieces are fit to look good. We may use measurements as a jumping off point, but it isn’t uncommon to trim a bit here and plane a bit there.
When I am in the shop, I always have a tape measure hanging off of my pocket for anything that needs to be measured. I use it a lot, but mostly for rough measurements, like making sure a piece of wood will be big enough for what I have in mind. I also use it for more critical measurements, but I try my best to find ways to not use measurements when things start to get critical. For example, instead of measuring, I will use a scrap piece of wood as a spacer. That way I don’t need to worry every time about reading the tape measure wrong, and I know that all of my spacing will be very consistent.
As much as I try to avoid being fussy about my measurements, sometimes they need to be a little more accurate. One of the tools where accuracy is important is the planer. If I want 1″ thick wood, I want to know that it is 1″. Now, more engineery people might reach for their calipers, but for those of you like me, with only a tape measures on your belt, I have a very accurate way to make perfectly sized parts – just stack them up.
Here’s the logic. If your measurements are just slightly off, you may not notice it in just one piece, but as you add up the pieces you also add up the differences and they become much more obvious. Just run a scrap piece of wood through the planer, chop it into 3, 4 or 5 pieces, stack them up and measure them. 5 pieces of wood that are 1″ thick should measure 5″ – simple de dimple. If your 1″ thick board isn’t exactly 1″ thick, you will see it, even without calipers, and then you can adjust the thickness.
The beauty of this system is two-fold. First off, you don’t need to worry about having calipers (after all, those are for kids that work at Boeing and have really clean floors). Second, it gives you a more accurate real-world reading of what is coming out of your machine. We all know that a board coming out of the planer has dips and doodles in the wood and can range in thickness depending on the spot that you measure. Adding up several pieces of wood gives you not only a measurement that is accurate, but it is also closer to the average. We are only talking small amounts here, but if you are setting up to plane a bunch of lumber, it is great to know what the bulk of it is going to measure.
I use this system to double-check measurements on other tools as well. It works great on the table saw to make sure that your 3″ wide board is really 3″. Instead of cutting just one sample board 3″ wide and determining that it looks really close, cut 3 or more and add them up. Assuming that you can do a little simple math, you will be able to tell if the 3″ mark is consistently spitting out 3″ boards and not 2-63/64″ boards.
When using my fancy measuring shortcut, there is one important rule to follow. Make sure the tongue on your tape measure is accurate or don’t use the tongue at all. If you don’t trust the tongue on your tape measure then take a reading starting at the 1″ mark to check the distance and then just subtract 1″ from your reading (and then hope that a holiday is quickly approaching that might lend itself to the arrival of a new tape measure).
On a regular basis, probably at least once a week, someone contacts me looking to have a pin oak milled into lumber. They are excited because they finally got their hands on a truly giant specimen of a tree, and even though it is just a red oak, they are excited to get to work with a hardwood at a reasonable price. Unfortunately, I have to be the bearer of not-so-good news and try to get them to reconsider.
As I mentioned, pin oak is in the red oak family, but that is about the only relationship it has to any decent red oak lumber. Pin oak is not milled and sold commercially under the name red oak, and as far as I know, is only used for low-grade products like pallets and blocking, where the only requirement is that it be made of wood that will stay together. And funny enough, pin oak often falls short of even that low requirement.
The problem is that many pin oak trees suffer from ring shake, which is where the rings of the tree peel apart like an onion, making that section of lumber nearly unusable. The beauty of ring shake is that it can’t be seen from the outside of the log and it won’t always be visible even early in the milling process. Sometimes, it won’t be until the lumber has been fully processed and dried for it to start falling apart. Needless to say this is frustrating, especially if you are counting on that lumber for a project and then end up with no wood to work. Even if the ring shake isn’t bad enough to make the lumber actually break, it very often leaves at least one fancy break line somewhere in a board where you would rather not have it. Again, super frustrating.
So, let’s say you find a pin oak that is solid, with no ring shake, then it is all clear sailing, right? Far from it. You may have lumber, but you probably don’t have great lumber. One of the main attractions for pin oak is the giant size and the promise of a never-ending bunk of lumber comprised of super-wide boards. This, you may indeed have, but it comes at a cost. The cost is that all of the super-wide lumber will have super-wide growth rings, rings that may be up to 1/2″ or more in width. Because the tree grows so fast, putting on up to 1″ in diameter per year, the logs get big in a hurry too. It isn’t uncommon for a 36″ diameter log to have only started growing 45 years ago. It was planted because the trees grow to a large, stately appearance quickly, and that means big, wide growth rings.
Big growth rings mean a coarse textured wood, no matter how you cut it. Whether flatsawn or quartersawn, red oak is already known for its open, in-your-face, grain, and pin oak is ten times worse. Imagine an 8″ wide flat sawn board that may only show a couple of annual rings on the face. It looks more like the cheapest of spiral cut plywood for sheathing the side of your house, instead of quality hardwood lumber for building fine furniture. That same 8″ wide board, if quartersawn, will probably show about 20-25 rings, where a high quality white oak board will show 60-80 rings. The difference is night and day, with the higher growth ring count looking much more refined and not so clunky.
Even if the wood stayed together and for some reason the growth rings weren’t so wide, pin oak would still be far from a great hardwood. The lumber typically also sports bad color, bad smell (commonly referred to as “piss” oak by local tree guys), and many more knots than are outwardly apparent. Since the trees are usually open grown and well pruned, the always straight, always perfectly upright trunks appear to contain up to 30′-40′ of clear lumber. The truth is that the trunks typically contain only 8′ of clear lumber near the ground, with the remainder being full of knots from previously trimmed branches.
Overall, I have nothing good to say about pin oaks, except that they grow big, tall and straight. And, while it may be possible to mill pin oak lumber that meets some minimum requirements (like staying together), the best pin oak is still easily surpassed in quality by almost any other reputable wood. Just know, if you are thinking about paying someone to mill a pin oak tree for you, that I wouldn’t even mill a pin oak if it magically fell on my sawmill. I would take the extra time to get it out of the way, so I could mill something better. It’s just not worth it. Move on.