Woodworking Tips
Woodworking Tips Index
Drawing Arcs

There's a number of ways to transfer an arc onto your workpiece. For example, when I want to draw a small radius arc on the corner of a project, I reach into my toolbox and grab a socket to use as a guide, see the photo at right. The nice thing is, you probably have sockets to match just about any small radius you need to draw.

But what if you're trying to lay out a large arc. You'd need a giant compass, right? Not necessarily, there are a number of ways to do it. It all depends on the size of the arc.
 
Known Radius. If you know the radius of the arc you want to draw, you can make a simple trammel out of a strip of wood, see the drawing at left. One end of the trammel has a notch cut in it to hold a pencil. The other end has a hole for a nail that sets the radius.

Unknown Radius. If you don't know the radius of the arc but you do know its general shape, grab a thin strip of Masonite hardboard. Then all you have to do is bend the strip to the shape of the arc and trace around it, see the drawing below left.
 
And if you're laying out an arc with a radius that's too tight to bend a strip of wood around, try using an 1/8"-thick piece of plexiglas, see the drawing below right. It's very flexible and something you're more likely to keep around the next time you have to lay out a large arc.
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