How to Lay Out a Radius in Woodworking

Layout a radius of any size with a pencil and a stick.

Radius layouts are used in the production of woodwork arches such as transoms, doors, round windows or whenever a custom wooden arch is needed. Small radius layouts up to about 12 inches can be done with a hand-held compass or protractor. Large radius layouts can be done by hand with a small stick and a pencil using a trial and error process that utilizes the stick on a pivot point, with the pencil on the other end.

Things You'll Need

• Stick 1/4-by-3/4-by-36 inches
• Cordless drill
• Drill bit, 3/16 inch
• Plywood, 1/4-by-48-by-96 inches
• Finish nail, 1 inch
• Hammer

Instructions

1. Drill holes in the stick with a cordless drill centered down the full length of the stick, 1 inch apart.

2. Insert a small nail through one of the holes in one end of the stick. Lay the stick on a 1/4-by-48-by-96-inch sheet of plywood. Lightly tap the nail into the plywood with a hammer so that the stick will still move freely on the nail.

3. Insert the tip of a pencil into a hole on the other end of the stick.

4. Hold onto the pencil with your fingers. Sweep the stick over the plywood, letting the pencil draw the radius as the stick moves in an arch over the plywood.

5. Place the pencil in another hole to make the radius bigger or smaller.

Tips & Warnings

• Once you get the arch to the approximate size you want, you can fine-tune it by drilling holes at closer spacings. For a really big radius, use a longer stick and lay down two or more pieces of plywood or draw it on the floor.