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Straight Talk About Circles

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Straight Talk About Cirlces
Straight Talk About Circles

Straight Talk About Cirlces

First, have a little bit of Pi

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.)

Handy circle calculations

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.

Set your compass, and lay out some circles and arcs

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.

Straight Talk About Circles

Continued on page 2:  Finding the Center


Comments (5)
booker brooks wrote:

A paint can - you have many sizes in your shop - set on the wood until each side is the same distance from the corner, will have you going is super fast time. No paint cans, use water glasses or anything that is round in your view. Nuff said.

2/26/2010 12:10:54 PM Report Abuse
2ward2 wrote:

The beauty of the demonstrated method, based on high school geometry, is that any size circular arc can be generated. The other suggestions either limit the arc to a "popular" size or require a separate template for each size. Using a compass can get you close enough to use a jig saw etc., then plane/sand off the remainder.

2/26/2010 10:24:28 AM Report Abuse
southernwayok wrote:

they also have a thing called a circle template that you set over the corner and draw the line.

2/26/2010 09:25:52 AM Report Abuse
acf3838 wrote:

to cut radius with a router I made conner pieces wiht radius cut on one end only an a stop clip on the other conner,1/2",3/4",1", 1-1/2" are the most popular size,just clamp over the conner use a router bit with a top bearing works great every time an fast.Fred

2/25/2010 03:46:45 PM Report Abuse
mrtilly wrote:

For a 1" radius corner you could run a 1" mark parallel to each edge and put the piont of the compass where the lines cross to swing the corner arc.

2/25/2010 10:24:03 AM Report Abuse

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