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Oh, Those Easy Edges

One might spend a lifetime working with wood and never know why dimensional lumber has those rounded edges. Somewhere along the history of lumber production, someone decided it was a good idea to round-over the edges of lumber, but why? What was the "original" reason? Ask five people and you are likely to get five different answers, none of which, or all of which, could be correct and all of which, or some of which, may simply be tangential benefits. I'm looking for the "original" reason though, not the corollary benefits.

Figure 6 - The end of this 2 X 6 shows the typical rounded, or "eased," edges common on construction lumber... ever wondered why the sawmills do this?

Of course, the rounded edges on a two-by-four are less likely to inflict splinters when handling, but I suspect that is just a secondary benefit, not the original reason. Let's face it, way back when… when lumber was sawn by hand by tough men with strong arms and heavily callused hands… splinters were of little concern and production was paramount. Would hand-sawyers really waste time rounding the edges of a board so as to avoid a splinter down the production line? I rather doubt it.

Likewise, when water-powered, and later steam-powered mechanical saws, took the place of hand-powered saws, I doubt that wasting precious power and time on rounding the edge of a piece of lumber was of paramount consideration.

Another theory of how radius edges came to be is that sharp corners on a board are quicker to catch fire than a rounded edge, so forming a radius on the edge of a board became the norm for fire-prevention purposes. This sounds like a plausible theory, and might be right. But in my research, I could find no early laws or codes that mandated eased-edge lumber, not that those regulations don't exist now. Fire protection, I think, is just another side benefit.

During stacking, transport, unstacking, and handling, the rounded edges of construction lumber are less likely to be damaged. This is the main reason we ease the edges of tabletops, shelves, and cabinet sides. But of all the reasons, this one seems most likely to be merely an added benefit. Why would a sawmill worry that much about what happens to a board once it is sold and leaves their factory? The process would add cost without much inherent received value… in other words, what sawmill could charge more for their lumber because it has a radius edge?

Framed walls with slightly out-of-square timbers would present a sharp edge when the face of the lumber is not perfectly square to the plane of the wall, so drywall could be damaged during installation. A rounded edge lessens drywall damage, even when studs are not perfectly square. The problem with this being the "original" reason for easing the edges of lumber is that mills were rounding edges on lumber long before drywall became transcendent, replacing plaster and lath.

In a production mill, lumber is run at high speed through a planer that smooths the board faces and adds the slight round-over on the edges all in one pass. As the knives in the planer begin to dull, the rounded over edge becomes less rounded, smaller, and sharper. One mill worker told me that the size of the round over is his gauge as to when to change planer knife blades. Okay, that is a smart observation and internal use for a rounded edge, but it is clearly a tangential benefit, not an "original" reason.

At another sawmill, the manager admitted that in today's world, the chips and sawdust produced from sawing, planing, and rounding the edges of a piece of lumber produce more margin dollars for the mill than the lumber itself. All those chips and dust get sold to other producers for making everything from particle board to fuel pellets to horse bedding. An excellent side benefit, but not the original reason for shaving extra wood off a board by rounding the edges. Back in the old days, sawdust and chips were "waste," and disposing of it was expensive and troublesome and it was a fire hazard… why produce incrementally more chips and sawdust by rounding the edges of lumber?

Try as I might, I can't find the "original" reason for easing the edges on production lumber. It appears that original rationale has been lost to the mists of history and generational memory. I liken it to the question, "Why do we cook our food?"

You can come up with a hundred reasons to cook food, but none of those get to the "original" reason… why did humans start to cook their food? I can conjure up mental images of a cave-person curiously approaching a fire started by lightning while holding the leg of a deer he or she is consuming. He reaches toward the fire with the deer leg, sort of "checking it out." The meat gets a little warm, maybe even tinged brown, it crackles a bit, and a wonderful aroma wafts toward our imaginary caveman. He pulls back the deer leg, takes a bite, and says, "Wow, that's good!" News of the taste and smell of heated meat spreads like wildfire throughout the cave-person community, and pretty soon everyone is "cooking." In a mere few thousand years, Martha Stewart and Jacques Pepin, who otherwise might be unemployed, have thriving careers showing us how to cook. And today we just "know" why we cook food… it tastes better, cooking kills parasites and bacteria, cooked food doesn't spoil as quickly, and on, and on, and on. Not original "reasons," but excellent corollary benefits.

Figure 7 - The "easing" of the edges of this cedar 2 X 4 is less pronounced, but still noticeable. I'll be getting rid of those round-overs as the first step in my new project.

As an experienced and knowledgeable woodworker, should someone ever ask you why the edges of construction lumber are rounded, just be honest and tell them, "No one knows… it's a mystery."

Speaking of construction-grade lumber with eased edges, that is exactly what I will be using in the next Down To Earth Woodworking video series… and the first thing I will do is get rid of those rounded edges and make nice sharp corners! Please join me as I build a Cedar Garden Potting Bench, a surprise gift for my neighbor, and something you should build for yourself or any friend that loves to garden!

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Steven Johnson is retired from an almost 30-year career selling medical equipment and supplies, and now enjoys improving his shop, his skills, and his designs on a full time basis (although he says home improvement projects and furniture building have been hobbies for most of his adult life). Steven can be reached directly via email at sjohnson@downtoearthwoodworking.com

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