The geometry on square or rectangular woodworking projects is pretty easy to figure out. But when it comes to round projects, like round tables, it’s a little more difficult. This woodworking video shows you how to lay out the project on a piece of scrap plywood so you know everything you need to know before you cut the first piece of project material.
Do the layout on a piece of plywood that’s larger than the diameter of the project you’re planning. You’ll need a large compass to create the circles. A beam compass is the best tool for this job.
Draw the circles that define the top, legs, and rails of your project. I find it easiest to mark the dimensions on my plywood and set the compass to the marks, rather than setting the compass to dimensions on a ruler.
Draw two perpendicular lines on the center of the circle. This creates four quadrants. Divide each of the four quadrants into two to create 45-degree subsections. You can easily divide the quadrants by using the beam compass to strike a short arc using the intersection of the quadrant lines and the circle as a center point. Connect the intersection of the arcs to the center of the circle. These lines indicate where two rails are joined.
Lay out the position of the leg faces. This is done by measuring out from the centering lines ½ the thickness of the leg.
The next task is to calculate how long the rails have to be to make the circle the round table requires. This is done by striking a line from the inner leg face to the 45-degree degree joint line. Remember that the inner most circle that you drew represents the curve of the rail. This circle must fall inside the line you draw from the leg face to the 45-degree line. Move the line equidistant from the center of the circle until, when you draw the straight line, the rail curve is inside it.
Calculate the angle at which the rails have to be cut by dividing 360, the number of degrees in a circle, by the number rails. Divide this number in two since you’ll be cutting half the joint on the end of each rail.
Determine the final rail length by measuring the length of the line that defines the rail, measuring from long point to long point.
Cut the rails to the correct length and angle and glue them together in pairs.
Using double-faced tape, place a block in the center of the circle layout that is nearly the same thickness as the width of the rails. You’ll also need spacer blocks that are the same thickness as the legs.
Temporarily clamp the rails and leg spacers together using a band clamp. Using double-faced tape fasten the rails to the layout. With the beam compass set to the correct radius draw the rail circle on top of the rails. Cut and sand the curve, resulting in a circle of perfect diameter for your project.