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Cutting Curves With a Router
From "Clamp Basics and more!" Episode DIT-121

This simple jig directs your router to cut perfect circles.
Figure A
Figure B
Figure C
Figure D
Figure E
Figure F
This jig guides the router to cut almost any size circle or arch.
Figure G
Figure H
Figure I
Figure J
Figure K

Many projects require cutting a perfect circle or an oval, and you can accomplish the task with a router and a special jig to guide it. The two jigs described below can be used with a router when you want to cut circles or angles.

Circle-Cutting Jig

The first jig acts as an arm that guides the router in cutting circles or arches.
Materials:

36" x 14" x 1/4" plywood
Drill and drill bits
Router
Screws
Ruler or measuring tape
Hammer
Nail

1. Take off the sub-base of the router to determine how big the circular end of the jig should be. Cut the end of the piece of plywood into a circle the same size as the router's sub-base (figure A).

2. Drill holes into the circular end of the jig to correspond with the holes in the sub-base. Use the sub-base to guide your drilling.

3. Screw the circular end of the jig into the router's base, aligning the circles on the sub-base with the holes drilled in the jig (figure B).

4. Drill small pivot holes into the arm of the jig, spaced 1" apart (figure C).

5. To use the jig to cut a circle, draw a line on the work piece from its center to the end of the desired radius of the circle. Center the router atop the end point of the radius. Drive a nail through the appropriate hole in the jig that corresponds with the center of the work piece (figure D). Set the router to the proper depth, and make a slow pass through the work piece, using the nail as a pivot point (figure E). Make deep cuts in several passes, lowering the router bit slightly after each pass.

Curve- and Circle-Cutting Jig

The second jig for cutting curves and circles with a router can be made from scraps you probably have around the workshop. Like the jig described above, it's attached to the router's sub-base.

Materials:

Two dowels, each about 2' long, with the same diameter as the holes in the sides of the router's base
Drill
Drill bits of same diameter as the dowels
12" x 4" x 1" wood block (dimensions need not be exact)
Sandpaper
Wood glue
Router
Hammer
Nail

1. Drill holes the same size as the dowels into one long edge of the wood block (figure F). The holes should be as far apart as the diameter of the router's base.

2. Sand the tips of the dowels (figure G).

3. Apply a little wood glue to the holes in the wood block (figure H). Place the dowels inside the holes, and allow the glue to dry.

4. Place the dowels through the holes on the sides of the router's base (figure I).

5. To use the jig to cut an arch or a circle, nail the center of the block to the center of the desired circle (figure J). Slide the router to the appropriate spot on the dowels to correspond with the end point of the desired radius. Set the router bit to the appropriate depth. Slowly swing the router through the work piece, using the wood block as a pivot point (figure K). Repeat the process as necessary, slowly lowering the bit with each pass.