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Circle Cutting Jig for a Router

Circle Cutting Jig for a Router

It’s not often that I need to cut circles larger than what I can accomplish with a hole saw, but every once in a while I have a project that calls for it.  Sure, a jig saw or a band saw will work, but if you are like me, it’s a challenge to cut a perfect circle.  That’s where a simple jig for your router comes into play.

To cut a circle with a router you basically need to have a leg to mount your router to with a means to anchor the assembly to a fixed center point.  This creates two points of a radius.  When the jig is rotated around the center point then a perfect circle is created.

I started with a piece of 1/4 inch acrylic and ripped it to the width of my router on the table saw.  I think it is about 18 inches long.  That’s too long.  About 12 inches would be ideal.  Then I made it mount up to my router.  I used a forstner bit to recess holes for the mounting screws so the jig would lay flat on the material I would be cutting.  Then I used a hole saw to cut a large hole for the router bit to go through.

Circle Jig Router Mounting HolesCircle Jig Router Mount 2

Circle Jig Pin HolesThen I marked the center line of the jig and router.  I mounted the router to the jig and put a 1/4 inch straight cut bit into the chuck.  I selected this size because that is the size bit I will routinely use to cut holes with this jig.  It’s kind of important to make a decision on the size bit because that will affect the next step, measuring for the radius anchor points.

To do this you need to carefully measure from the outside cutting edge to the centerline on the jig.  For example, measure back 2 inches and make a mark.  That mark represents a 2 inch radius, thus it will cut a 4 inch hole.  I made several of these measurements in 1/4″ increments so I can cut holes in 1/2 inch increments.  I took the jig to the drill press and drilled 1/8 inch holes through the jig.  If there’s ever a need to cut a hole on a 1/4 inch or other increment I can simply drill the corresponding hole for it.  This hole will have an 1/8 inch pin that will go through it and into the material being cut to anchor the jig in place.

The jig turned out great and it works really good.  In fact, I used it on the Willys Jeep Grill project and it made all the difference in the world.  Sure, you can buy these things and they are a little more polished and slick, but for a fraction of the cost you can build one of these fine redneck engineered circle cutting jigs.  For a more detailed explanation and step by step instructions on how to build one then take a look at my Circle Cutting Jig Video.  Rock on…..

Circle Cutting Jig