Straight Talk About Circles

Straight Talk About Cirlces

If you're going to deal with round things, you need to know about p (Pi). Pi, a number you'll use often in circle calculations, represents the number of diameter lengths of a circle it would take to equal the same circle's circumference-about 3.14159. About, because p is always approximate-its value has been calculated to more than 2.2 billion decimal places without ending or repeating. (Many calculators have a p key to make figuring simple.)

On the last page, Anatomy Of A Circle, you'll find some formulas to help you solve workshop problems involving circles. Using the circumference formulas, for instance, you can determine the length of veneer or laminate you'll need to edge a round tabletop. Or, if you know the distance required around a circular table to provide certain seating capacity (the circumference), you can easily figure the table's diameter by dividing by p. Area calculations come in handy when you're estimating finish coverage or material quantities.

Project plans and instructions ordinarily specify the diameter for circular parts. The radius usually is called out for corner rounds and other arcs (parts of circles). You already know how to draw a circle of a certain size: Set the distance between your compass legs or trammel points to the radius of the circle (half the diameter), and draw around the center. To avoid pricking the center with the compass point, stick on a piece of masking tape. You can lay out a corner radius just as easily, once you locate the center. To find the center and lay out a corner round in just three steps, first set your compass to the corner radius specified. Then, follow the steps in the photos below.