If you want gap-free joinery and a perfect, long-lasting fit for both strength and aesthetics, precise measuring and marking of parts is essential. But, each step of the process — measuring, transferring marks, and cutting — can introduce tiny little errors of 1/64 or 1/32", which, over the course of a project, can add up significantly. So here's a simple little trick that takes no extra time, but creates much more accurate results.
If you do woodworking and DIYing in inches, a solid understanding of fractions is essential. Being able to calculate that half of 4 1/4" is 2 1/8", or that 1 1/2 + 1 3/16 = 2 11/16" is basic shop math that will keep your projects moving quickly.
But often, bringing fractions into the process is, well, completely unnecessary. Let's say you have a board that you'd like to divide into equal parts. You could measure it, then bust out a pencil, paper, and the calculator app, and eventually have to Google a decimal-to-fraction converter to figure out the size of each section. Then, you'd have to find that crazy number on your ruler, and carefully add the units together to mark out your parts. Or... you could just do this.
Often, when it comes to DIY projects, we create our own circles by starting from a center point. Whether a compass, string guide, or specialized cutting jig, a circle emerges from our pencils or saws precisely because we've created an established and consistent distance from a single origin.
But, what happens when the shape already exists, and you need to know how to find the center of a circle? You can do it in less than a minute without any specialized math, memorizing a formula, or even knowing what pi is.
Among all the items in my shop, the measuring, marking, and layout tools are probably my favorite. Mostly, I love how historic they are: dividers, squares, calipers, rulers, and marking gauges have all been around for centuries, remaining mostly unchanged in their design and intended purpose. And who doesn't love a clear, crisp, and accurate line to work to?
Proper and accurate measuring and layout are key to a great looking project. When you're dealing in whole numbers, that's easy enough. But the smaller you divide those inches or millimeters, math becomes more complicated, and the likelihood of making a mistake increases. While we can't always avoid finding common denominators and doing sophisticated shop calculations, when you're trying to lay out evenly spaced marks, you actually don't need math at all.