Things You'll Need
1 piece of plywood, 36-inch by 10-inch by 1/4-inch
1 drill bit, 1/16-inch
Ruler or yardstick
Various home projects call for cutting shapes out of pieces of wood and not all of them have straight lines. Some home projects require cutting out circles using free-hand tools such as routers. Depending on the project, a perfectly circular hole will improve fitment and make the end result look more professional. Circles can be a difficult shape to get right, and cutting circles requires a jig to do it correctly.
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Making the Jig
Remove the screws holding the base onto the router.
Place the circular router base at one end of the plywood and trace the circular edge of the base with a pencil.
Mark a 3 1/2-inch section of the circle's edge that is opposite of the end of the wood. This will form the handle or pivoting arm of the jig. Use the ruler or yardstick to draw the sides of the 3 1/2-inch pivoting arm from the circular end to the opposite end of the wood.
Cut out the circle and pivot arm of the jig using the jigsaw.
Mark the circular end of the jig corresponding with the holes in the base of the router. Drill the holes through the jig.
Mark the jig using the central hole of the router base that the router bit goes through. Use the router to create this hole.
Mark the pivot arm of the jig with holes down the center of the arm. Space the marks 1-inch apart down the length of the arm from the circular end to the opposite end. Drill the holes.
Attach the circular end of the jig to the router base and reattach the base and jig to the router, jig-side down. Longer screws may be required to go through the base and jig into the router.
Cutting the Circle
Draw a straight line from the center of the work piece to the end of the required radius of the circle. Place the center of the router over the end of the radius.
Drive a nail through the hole on the arm of the jig that corresponds to the center of the desired circle. A new hole may be nailed through the jig if a corresponding hole doesn't line up.
Adjust the router bit to the desired depth. Make one slow pass around the piece using the nail as a pivot point.
Make several more passes lowering the bit-depth each time.
If longer screws are required to fit the jig and base back on the router, use properly fitting screws to avoid stripping the holes in the router.
Always wear proper protective eye and ear equipment when using power tools.