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.
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.
My sawmilling adventures began with an Alaskan chainsaw mill, which is just an attachment for a chainsaw to allow it to repeatedly cut a log lengthwise into lumber. It wasn’t anything fancy, and while it produced fine lumber, it was painfully slow to use. It didn’t take too many hours of me directly sucking in sawdust and fumes, while sweating my butt off, to start shopping for a more capable sawmill.
When I started my search, I considered bandsaws made by companies smaller than Wood-Mizer or TimberKing or Baker in a quest to also find smaller prices. While searching, I found several mills that looked suitable in the $5,000-$10,000 range, and I also came across a new “swing mill” from Australia called a Lucas mill.
The bandsaws looked to be a good choice as far as production went, but I didn’t have any way to move logs at the time, so the Lucas won out. It’s ability to easily break down and set up on site, while fitting in the bed of a pickup truck made it the clear choice, especially for larger logs. I say clear choice, but it wasn’t an easy choice. I didn’t like that the basic mill, fitted with a circular blade, was limited to 6″ or 8″ wide lumber without the optional slabbing bar attachment. And, my biggest fear was that this new mill from Australia, that I knew nothing about, might not be as good as it appeared in the videos.
Unfortunately, my fears were NOT immediately allayed. I went to pick up the more than $10,000 sawmill at the shipping terminal, and I couldn’t help but feel like I way overpaid for the amount of merchandise I picked up (Did I mentioned that it fits in the bed of my pickup truck?). There was only a sawhead, two long rails, and a few other miscellaneous metal parts that formed the frame ends. Besides that, the kit included a sharpener and some other odds and ends, but none of it added up to very much. I started doing the cost per piece arithmetic in my head, and it wasn’t looking good.
Regardless of my buyer’s remorse, I was tickled to have a “real” sawmill and set it up in my back yard the very first chance I got. After just a short time reviewing the directions, I had the sawmill set up and ready to cut. Even for someone who had never set one up, the Lucas went together fast. It was then that I realized what I had paid for. I didn’t pay for lots and lots of parts and extra bulk. I paid for an impressively designed machine, with an amazingly small stature, than can tackle the biggest logs. I paid for all of the research and design that went into the mill by the Lucas boys, and I paid to not lug around thousands of extra pounds, and I paid for everything to go together with minimal effort and a minimal number of steps. I got all of that and more.
From a design standpoint, I can confidently say that every part of the Lucas mill is well-planned and simplified beyond belief. The only mechanisms that I have ever had a problem with are the winches that raise and lower the ends of the long rails. They work perfectly fine and they are quite smooth, but they can be dangerous. When fully loaded with weight, it is possible to release the winch and lose control, resulting in a violently swinging handle that can smash your arm and allow the sawhead to come crashing down. I know from personal experience, as this has happened to me more than once, with the last instance leaving me at the hospital with a possible broken arm (luckily it was just a very bad contusion). If they were to ask, I would recommend that the winch system be built like the raising and lowering mechanism on my TimberKing 1220 manual mill, which magically is able to easily raise and lower the sawhead with complete control and without the possibility of having a disastrous crash. I have no idea how it works, but it smoothly operates the sawhead with a very heavy 15 hp electric motor attached to it like it isn’t there at all.
Now that you know to watch your arm and to be careful when lowering the sawhead on the Lucas mill, I can continue telling you how wonderful the Lucas mill is. First off, realize that I bought a Lucas mill in 1995, so I have been using one for about 2o years now, and I still use it on a regular basis. It is a very versatile machine that can handle big logs with ease. I often get asked how big of a log I can handle, and with the Lucas mill in my corner, I can just answer, “Yes.”
Currently, I use the 8″ model, which means that with the 21″ diameter circular blade attached it can produce up to 8″ x 8″ dimensional lumber. I rarely cut 8″ x 8″, but the mill can easily be adjusted to cut any dimensions under 8″. I often cut 1″ and 2″ thick lumber by 8″ wide.
The Lucas mill is called a “swing” mill because the blade can flip or swing with the pull of a lever from the horizontal to vertical position and right back again. The cool part is that both of the cuts line up with each other and work in concert to produce accurate and straight, completely edged lumber without a dedicated edger or any extra handling. In contrast, to edge lumber on a bandsaw mill requires flitches (lumber with bark edges) to be stood up in the mill and cut one or two more times to produce lumber with four square edges.
When cutting dimensional lumber I can easily work by myself making the vertical cut walking backward, then making the horizontal cut walking forward and finishing by sliding the cut board backward and out of the way. After a quick repositioning of the sawhead and a flip of the blade, I am back to cutting another piece of lumber. When cutting dimensional lumber like this I get in a rhythm–walk backward, flip blade, walk forward, slide board, move and flip blade, then repeat. The first cuts on the outside of the log are firewood, but after one pass across the top of the log and then dropping the mill to the next set of cuts, almost every pass produces an edged piece of lumber.
When I first got my Lucas mill I used it with the circular blade most of the time. Everything I produced was fully edged. Big slabs weren’t in style, so I didn’t even own a slabber, let alone use one. Now things are different. Live edges are in and so are big slabs, so the slabber is on the mill most of the time. The slabber is an attachment that turns the sawhead into a giant 2o hp chainsaw mill, with a maximum cut of 64″ wide.
I use the Lucas mill with the slabber attachment to cut all of my big logs that will produce slabs for table tops. With the slabber attachment the Lucas is not fast, but it can cut much wider than my bandsaw mill (maximum cut of 29″ wide), and it doesn’t make sporadic wavy cuts like the bandsaw mill. Knowing that I won’t get a miscut on a high-priced piece of wood gives me a great piece of mind.
These days when the slabbing attachment isn’t on the mill, the circular blade is, but not for milling lumber. I have been using it to flatten my kiln-dried slabs, and as long as the blade is sharp, it works great. After I move the slab into position, I just skim the surface with the mill to remove the high spots. Next, I flip the slab, drop the mill a bit and skim the other side. The end result is a perfectly flat slab, ready for final planing. The kids at Lucas sell planing and sanding attachments, but I haven’t used or purchased either one since I finish almost all of the slabs with the power hand planer or wide-belt sander.
Every time I use the Lucas mill, I am reminded how well it works, from quickly setting it up to making small adjustments, everything is simple. And, I know when I show customers how capable it is, they are impressed that such a lightweight, easy-to-setup mill can do so much.
Note: While Lucas is more than welcome to pay me to endorse their mills, as of now they do not. This was written for educational purposes and to let others know how my slabs are produced.
Most woodworkers that I have met, try to finish their own projects, and while they may do great woodwork their finish often falls short and lets the world know that their project was not finished by a professional woodworker or finisher. The typical look of the less-than-perfect finish is one of obvious and often errant brush strokes. While I think it is possible that some of these finishing jobs are seen as perfectly acceptable by less discerning eyes, I would like to think that the applier of these lackluster finishes knows and sees that they could do better, but are at a loss for how to correct the problem.
My first solution, and always my first recommendation, is to purchase a high-quality spray gun and start spraying your finish. A spray gun is quick, capable of producing a flawless finish and may even make finishing fun. There are lots of reasons why you may not feel comfortable spraying a finish, but there are at least 492 reasons why you should spray your finish–the first 485 being that you need to be a badass to brush a good finish.
Brushing a good finish requires an amazing level of patience, attention to detail and a willingness to not cut corners. It can be done, but often the person that relegates themselves to brushing a finish is usually the same person that struggles to produce a good finish because they aren’t patient, aren’t paying close attention and are trying to do as little work as possible to call the job done. It is a crazy irony of a situation, but it happens all the time.
Now, first let me be clear, I don’t have a problem with brushing a finish. I think it is perfectly acceptable and sometimes required, but it has to be done right just to not look bad, never mind looking great. Luckily, there really are just a few tidbits to keep in mind that are the keys to a beautiful brushed finish.
Apply Thin Coats
You will be tempted, at all stages of finishing and throughout your entire life, to apply a finish that is thick and wet. Often this is under the misguided notion that thicker is better and it will speed things up, but nothing is further from the truth. A thick finish coat is the first and deadliest weapon in the unprofessional finishers arsenal. No matter how well you apply a thick coat of finish, it will somehow, somewhere on your woodworking be less than perfect and scream, “This dude doesn’t know what he is doing!”
Thick finish coats show deeper, more obvious brush strokes because they are just that, deeper. Thicker coats also tend to run and, at very least, sag. And, the last thing, that shouldn’t be underestimated, is that thicker finish coats take much longer to dry, which allows more debris to get in your finish, lengthens the dry time between coats and often leads to blemishes from handling a piece before it is dry. There is, as far as I can tell, nothing to be gained by brushing on a finish in thick coats versus thinner coats.
Applying thinner coats can and should be thought of in two ways. The first is simply the amount of finish moved from your brush to the surface. When applying the finish, put on just enough material to cover the surface and nothing more – do not leave puddles. There should be so little on the surface that it is impossible for the finish to run or sag. The second way to think about thinner coats is in the viscosity or the thickness of the material itself. Thinner material will flow fast, like water and thicker material will flow slow, like syrup. Make sure your finish is not too thick by adding the proper solvent for your finish, like water, mineral spirits, alcohol or lacquer thinner if needed. Many finishes will be fine directly out of the can, but some thicker finishes will benefit from a little thinning. Be sure to read the can for proper thinning options and test your finish on a piece of scrap material first to see how it flows and lays down.
Pay Attention to Your Brush Strokes
No matter how well you apply a finish with a brush, brush strokes will most likely be visible at some point. The good news is that wood has a grain to it that can help hide the brush strokes. The secret is to apply the finish with brush strokes that follow the grain. Don’t go all willy nilly and just slop it on. This is where the patience and attention to detail really come into play and where you have to let your inner badass shine.
Plan out your brush strokes so there aren’t any unintentional stops or starts. Where parts meet make sure to stop and start where they stop and start. On mitered corners, start with the brush at a 45 degree angle so the brush marks only follow the grain of each board.
Lastly, make sure that your brush strokes follow the full length of the work. If a single piece of wood is 30′ long, your brush strokes should be 30′ long in a single uninterrupted and reasonably straight pass. It may sound a bit overboard, but that is what it takes to do this correctly.
Keep a Wet Edge
Working with a brush is not fast. While you are messing around with the application and focusing on your brush strokes, it is possible for some finishes (especially paints) to start to dry while you are applying them, requiring you to step up your game even more. It is important to keep a wet edge while you are working, so each new brush stroke blends with the previous one. If you move too slow and the finish has dried or started to dry, you will basically be applying two coats as opposed to only one. If you are finishing woodwork, this will cause the finish to have an unevenness about it, either because of a difference in the sheen or in the way it fills the wood pores.
When working large open areas, plan out your approach and move quickly. Do what you can to quickly get the finish on the surface and then focus on your brush strokes to finalize things. A small-nap roller can even be used to help speed up delivery to the surface before final brushing. If you have a choice, work in cooler temperatures (always out of the sun) and with reduced airflow to slow down the drying.
Any finish application, whether brushed or sprayed will benefit from being horizontal. Having your pieces flat on a work surface during finishing allows you to fully see what you are doing, especially with good reflected light and helps the finish to level out while drying. The other obvious benefit is that you should get no runs on a horizontal application unless you are extremely talented. You may find it worthwhile to completely finish your piece before assembly so you can keep all of your parts horizontal.
Choose the Right Brush
There is much to be said about brushes, but for me it comes down to one simple rule. Don’t ever use a cheap brush. Don’t even let them in your shop. If you have a cheap brush in your shop (you know, the one that you were only going to use for applying glue or something else non-technical), you will inevitably end up trying to use it for some sort of real finishing and it will not turn out well. I would argue that it is better to not finish at all than to try to finish with the only brush you could find in the shop which was purchased in a 10-pack at the dollar store. Using a good brush gives you at least a fighting chance. For those of you that want a bit more technical input, remember to use natural bristles only for oil-based finishes and synthetic bristles for either water-based or oil-based finishes. It all comes down to the fact that natural bristles don’t like to be soaked in water and synthetic bristles can be soaked in anything.
There you have it. Five simple little rules, all of which if you completely follow, still only give you about a 50% chance of producing a beautiful brushed finish. The other 50% is dependent entirely on your willingness to not take anything that resembles a shortcut and on you being a badass every step of the way.
Through the years I have dulled a lot of bandsaw blades on my sawmill, and for the longest time, I have struggled with keeping them sharp. I have tried multiple tools and methods to get this done, but only within the last year do I feel like I have found a good solution.
The problem starts with the bandsaw blade itself. It is a finicky conglomeration of bent teeth, cut from a thin piece of flexible steel that is somehow supposed to cut a straight line, not only from front to back, but also side to side, and if it isn’t well machined and sharp, there isn’t a snowball’s chance that this is going to happen.
Early in my career, when a new saw blade dulled and started to cut waves, I would try things like adding tension to the blade, slowing down my feed rate or even adjusting my blade guides. No matter what I tried, a dull blade would still make a wavy cut. However, if I used the exact same setup but installed a new blade, the cut would be perfect again. As a matter of fact, almost every other adjustment could be less than perfect and a sharp blade would still make a good cut. From 15 years of experience, it is clear that I need to keep my saw blade sharp and touch nothing else.
My standard course of action is to put on a new or newly sharpened blade from Wood-Mizer when my cut starts getting wavy. This is a great way to live. Nothing cuts like a brand new blade, and it feels like a treat to put one on. Even the resharpened blades cut great since they get a complete factory treatment, including cleaning and full tooth grinding and setting. I have always had great results from Wood-Mizer, and I highly recommend their new blades and resharpening service. (Disclaimer: I am not being paid by Wood-Mizer and Wood-Mizer doesn’t know I’m writing this post – they probably don’t even know I exist.)
The problem for me was that time in between cutting like new and cutting like crap. I would have a blade that was cutting great, but I could feel it pulling hard and on the verge of cutting poorly. I didn’t want to pull it off of the saw because it was running so well, but at the same time I knew my time was limited. If I could just get an edge back, I could keep cutting with the same blade and not have to mess with sending the blade off to be sharpened, and I would save $7 (by the way, I think $7 is a great price for the quality of service, but I would rather not spend it if I don’t have to). So, off I went, looking for a way to sharpen blades on my own.
In the past, I tried using a manual sharpener that came with my first bandsaw mill. It functioned like it was designed to, but the results weren’t great. Besides having to take the blade off of the mill and set it up in the sharpener, it used a stone that wore down quickly and wouldn’t maintain a flat, consistent face on the tooth (looking back, I probably should have tried some other stone options, but I didn’t).
Later, I tried a few other approaches. The first was using my chainsaw grinder, like the one below, which had a similar problem to the first grinder. The small stones would wear down quickly and the thin bandsaw blade would basically cut the stones in half.
The next attempt used a sanding disc on a drill. I liked the idea of using sandpaper because it maintained a flat surface during grinding – it would wear down, but not change shape. This one showed potential, but it was incredibly hard to control because the spinning motion pulled the drill up and away from the blade.
I finally gave up, feeling like I had exhausted every option cheaper than buying a fully automatic grinder like the factory has, but I never gave up on the idea of sandpaper as a good abrasive that doesn’t change shape.
Up to that point, all of my attempts focused on sharpening the saw by grinding the front of the tooth. There was nothing else I could think of that would fit between the teeth and grind the front of them. But, then I thought about grinding the top of the teeth. This surface is easier to get to and taking material off of the top will still lead to a sharp point – it doesn’t really matter which face gets ground down.
I started off with my 3″ Porter-Cable belt sander just to try things out and it worked great. I could sand the top edge of the tooth with control and the speed was slow enough to not feel like I was burning the metal (which softens the teeth). The only problem was the weight of the belt sander, which might as well have been 1,000 lbs. because there was no way I could hold it to sharpen all of the teeth on the blade.
At the time I didn’t own a small belt sander, so I took a gamble and purchased a Porter-Cable 371 compact belt sander. I figured that even if it didn’t work for the blade sharpening I would at least have another tool in my woodworking arsenal and that there were going to be plenty of times when a small belt sander would come in handy. Finding other uses for the new sander hasn’t been much of an issue though, because it works great to sharpen blades, and it is always parked (plugged in) right next to my saw, ready for the next dull one to come along.
I simply leave the blade on the saw and grind just enough off of the top of each tooth to get the edge back. I use my free hand to steady the blade and to advance the saw to the next tooth. In a matter of just a few minutes I can be back to cutting, feeling like I have beat the system.
Now, there are limits to sharpening your saw like this. First off, no matter how good you get with the sander, the blade will not be as good as a new one or one that has had a full factory grind and set because this grinding is changing the geometry of the already finicky blade. And, it will do nothing to improve a blade that was just generally running badly or running badly for a specific reason like hitting a rock or metal (all of these problem blades get sent out for a full resharpening). It will, however, make a blade that was running well continue to run well and make flat, straight cuts for much longer.
Generally, it seems to work out that I touch up a blade with the sander a time or two and then send it out for full service or, for some of them, they keep working great and I keep sharpening them with the sander until they break. For all of the others, I hit something along the way (dirt, rocks, concrete, nails, hooks, cable, wire, screw-eyes, barbed wire, fence posts, screws, license plates, horseshoes, railroad spikes, chain, conduit, hangers) that either destroys the blade or dulls it enough that it needs a full regrind.
Even if I don’t use this method all of the time, it is nice to have another option to get back to cutting. If nothing else, I personally love the comfort of knowing that when I get down to my last new blade (and forgot for the second week in a row to order new ones) that I won’t be stuck cutting wavy lumber.
When customers stop by to peruse the lumber and slabs I have for sale, they inevitably end up near the back of my shop, where I do my woodworking. They like to see what I am up to and discuss woodworking in general. Lately, I have been making a lot of live-edge tops, so I usually have at least one being glued up, and I can guarantee you that the first question is going to be, “What do you use to join those two pieces of wood together?” They are expecting a dramatic answer full of technical jargon, like tongue and groove or sliding dovetail or dominos or even biscuits, but I always disappoint them and just say, “glue”. I like to say it in a sort of caveman fashion for dramatic effect and a bit of humor, but then I quickly jump in and fill the awkward silence with a more detailed explanation, especially since I can tell that just blurting out the word “glue” isn’t going to be enough.
I use Titebond original wood glue with the red cap. There is Titebond II and III for more water-resistency, but I usually stick to the original unless it is a project that is prone to getting very wet. I like that the original cleans up easily with water and that even dried glue can be soaked and removed from brushes and clothing. I don’t prefer Titebond for any special reason, except that it is widely used and widely available. I would just as confidently use other name-brand wood glues and expect similar results.
The glues available today are strong, super strong, stronger than the wood itself. To prove this, I always save the end cuts from my glue-ups, so I can break them later for demonstration purposes for customers and inspection purposes for myself. If the glue is fully dry (results are not guaranteed if the glue is still wet), the glued-up scraps will always break somewhere in the wood. Even if it does happen to spilt close to the glue line, there is always plenty of wood stuck to the glue to make anyone doubting the strength of the joint to become a believer.
In comparison, I have worked with plenty of reclaimed wood, especially old oak church pews, that have a tendency to split along the glue joints. When closely inspected, it is clear that the old glue had become dry and brittle, and though it stuck to both surfaces, the glue itself broke down, like old plastic that has been outside too long. Most likely, the older glues, while strong at the time, weren’t formulated correctly to stay flexible over time. Current glues are formulated to hold strong and not break down during regular indoor use. Note that I wrote “indoor” use – for outdoor use, all bets are off. From extreme wood movement to glue breakdown, there is simply too much wear and tear outdoors for the glue to hold a jointed edge together on its own without any eventual failures.
So, we know that the glue is strong and is more than capable of holding a joint together, but just how strong is it? There is probably some value on some fancy scale to tell you exactly how strong the joint is, but it doesn’t really matter, as long as you know that it is stronger than the wood. At that point, to know the strength for sure, you would need to know the strength not only of the wood you are working with, but the weakest point in any given spot in a board, which you just can’t know, so I say stop worrying about it. Just know that it is more than strong enough to do the job.
Now, for the glue to work correctly, your machining and joints need to be reasonably good. I say, “reasonably” good because I think there is a lot of wiggle room here. Obviously, if everything is perfectly square and straight, there is no question about your joint integrity. You can simply coat the joint with glue, apply just enough pressure to pull everything together, and you will end up with a strong, wonderfully impressive joint. But, what if your jointed edges are square but the boards are long and have a bit of a bow and they will require a bit of extra clamp pressure to pull them together, is that gonna work? Heck yeah! Did I mention the glue is strong? A little extra clamp pressure is fine.
What about a lot of clamp pressure? Now this is where the “reasonably” good part comes into play. I say if you are doing a glue-up and you feel like you have applied so much pressure to pull things together that it just feels wrong, then you should probably work on the joint some more. But, here’s the kicker. I can tell you that I have been involved in more glue-ups than I should admit to that have required an inordinate amount of clamp pressure, and to this day (knock on wood), I have never had a joint fail. Maybe I have just been lucky, since I have done tons of glue-ups, but I use this as a real world testament to the strength of the current glues.
The problem with needing a lot of clamp pressure to pull joints together is two-fold. The first issue is that there are built-in forces that are always trying open the joint with the same amount of pressure it took to close up the joint, which can be significant. The other issue, and the one that is commonly more worrisome, is that more clamp pressure means less glue in the joint. The concern being that if all of the glue is squeezed out then obviously there is nothing to hold the wood together. As far as I can tell, especially since I have not had a failure yet, is that this isn’t easily accomplished. I am not saying it isn’t possible, but it isn’t easy. Many woods have open pores that will hold glue no matter how much pressure you give them (think oak and walnut), and if you are fighting at all to pull a joint together, that means that somewhere along the line things are loose enough to hold some glue. Sure, it might completely squeeze out in one spot and make the joint a bit weaker, but in other spots the glue will hold like it is supposed to and keep things from coming apart.
With all of this cavalier talk about crappy joints with extra clamp pressure, you still have to show some restraint. There are going to be times when you can’t rely on just the glue, no matter how strong it is, to hold everything together and you will need to rework your joints for a better fit. A couple of instances come to mind. Some woods have very tight grain that is smooth and won’t hold much glue (think hard maple), so it is possible to end up with a joint that has almost no glue in it. The second instance where more jointing work will be required is if the boards are tight in the middle and loose on the ends. The ends are where a top will want to naturally split, so trying to use extra pressure in this case, is inviting an issue down the road. I feel a million times more confident closing up a gap in the middle of a glue-up than I do the ends, knowing that the entire joint is holding things together, not just the glue on the ends.
One last category that requires a little extra attention is exotic wood. Some have oils in them that just won’t glue properly. They need to be cleaned with lacquer thinner before gluing to provide a good surface and they are often extra hard, so they don’t absorb much glue. I have had problems with bloodwood in the past, which fell apart during my initial tests because I had not cleaned the wood enough. To be safe, I cleaned the wood even more and roughed up the surface a bit with sandpaper to give the glue something to grab. Before the sanding, the edges were just too hard and too smooth. Since then, the extra hard and oily exotics scare me, so I would never force a glue joint with them. I trust the current glues a lot, but there are limits.
Assuming that you have decent joints and wood that will accept glue, all you have to do is make sure that both surfaces are coated with wood glue and clamp them together until the seam is tight. That is really all there is to it and all that is done at almost every professional shop I can think of. You don’t need any special tricks at all, just “glue,” I remind you in my caveman voice.