I used to do woodworking as a hobby and making anything that’s both useful and that will last a long time is way harder than you’d think it is. Like oh just screw pieces of wood together, how hard could it be?
Well, that’d work temporarily maybe, but wood deforms as it ages, loses moisture content, and just through good old thermal cycling. The way wood expands and contracts is also not uniform, and they expand more in the direction of the grain than perpendicular to it. This has a lot of implications regarding joining pieces of wood together. The end grain also tells exactly how a piece of wood will warp and how likely it is to crack. You literally can look at the end of a board, see what part of the trunk’s cross-section it was cut from and know how it’s gonna warp as it ages and dries out. This makes some boards unsuitable in places where others would be fine, but you have to know what to look for.
If you’re making a table top and want it to be sturdy, a good method is lamenation or joining multiple boards together to form a larger surface. Frankly is this almost necessary because we don’t let trees get old enough to have trunks large enough to cut large slabs out of anymore, and the ones that are that big and get cut down are super rare and expensive as shit. 2x4s are relatively inexpensive and readily available so let’s say you wanna make a top out of those. If you want to join them literally together on the widest side, it’s ~2" thick and some multiple of 4" wide, you’re just asking for it get to warped all to hell because there’s the surface area you’re joining is so much smaller than the surface area of each board that can warp. The cheap solution (commonly used by like picnic tables and the like) is to fasten each board individually to a cross-beam on the frame. The warping of a single board isn’t going to distort the entire table as much and you can replace each board individually. It also requires much less time and effort to build which is why that design is really popular even though it’s not really good woodworking from craftspersonship perspective.
It’s much better (even though it’ll require a lot more boards) to join the 4" faces together, and the upper and lower faces of the top are composed of ~2" strips. However, that’s still not enough to avoid all the issues. You’ve reduced the impact the warping an individual board will have, but you haven’t eliminated it and you’ve added a lot more boards so things can still go very strong. The key now is to arrange the boards you’re going to laminate according to their end grain patterns. You want to place boards next to each such that their natural tendency to deform will fight against each other. Let’s say you have two boards that want to go from a straight line to one that curves. You take those two, and arrange them so they’re going to curve away from each other like an open and close parentheses ( ). When they’re glued up properly (and you want to use wood glue to join them together because those bonds are stronger than the bonds between wood fiber to itself), the edges push against each other, and the centers have way too much holding them together to push themselves apart. If you did it the opposite way, ) (, those edges (by nature of being edges) have the least glued surface area holding them together and will just pull apart as they settle and this isn’t really fixable.
But anyway that’s just the top of a table. Attaching things like legs and stuff seems like it should be simple right? Just attach the top of the leg directly to the bottom of the table. Well, that’s also wrong. You just attached two pieces with perpendicular grain direction. No matter how you attach the flat surfaces to each other, the table now wants to tear itself apart on a near daily basis. So then it’s one several methods of getting the top to sit on the legs without slidely freely or doing it in a way that’ll definitely make it a wobbly in a few years. All of this to make a fucking table.
The real kicker is I’ve seen a lot of old furniture that does all this. It’ll be nearly 100 years old and the wood will beat up to hell, but it’s still solid as a fucking rock and isn’t wobbly or anything. Some artisans were even clever enough to use a glue with a solvent that was unlikely to spill on it so they could even be repaired piece by piece if it really came down to it. I sometimes think that people portraying older civilizations as more advanced is silly (and the actual portrayal is often a bit absurd and requires some weird mysticism), but fuck me if it’s not visible in our current day not because of lost knowledge or anything, but because we’re shortsighted as hell. We see something that’s an order of magnitude cheaper than the high quality thing so we buy it, and when it breaks down decades before the alternative we just buy the cheaper one again. We do this over and over and over again until we’ve paid more for the cheap versions and wasted a lot more material, but it’s hard to conceptualize that because of the time scale. The skilled craftspeople that could make these comparative marvels that can last multiple generations in some cases go out of business or have to market themselves towards increasingly affluent clientele which further puts their goods out of reach. It makes me sad. I buy Ikea furniture because it’s so much cheaper than the “nice” stuff in furniture stores and because I’ve inspected the quality of the work, and it’s also mass produced mediocrity but pretends not to be. At least Ikea furniture doesn’t pretend to be what it’s not as much.
