Router Circle Cutting Jig

Introduction

Making circles is almost impossible to do free hand using a router. No matter how hard you try your diameters will never be 100% without the use of a jig or guide to restrict your router from straying off course. This router circle cutting jig is exactly the solution you need for this problem and I am positive you’ll wonder how you lived without it. Although the jig you will learn to make in this video is customized to my particular router it is very adaptable to any make or model. I have had this jig in my shop for sometime and although I made it in preparation for another project I can still see the potential for its use in many other projects. You can make it to suit as large a diameter as you like but its use and function will remain the same. 

The Build

I use some half inch Baltic birch plywood for this jig that I had left over from a previous project, you however can use any type of material you would like. I would stay away from anything thicker than 1/2" material because you may have to go to the hardware store and find longer screws to compensate for the added thickness.

Because the base plate of my router is needed for a few steps during this build I decided to remove it at the outset rather then later.

Before cutting to size I first mark the dimensions out on my plywood panel using my combination square and a pencil. I cut the panel to size using my table saw.

Layout is a large portion of this build and it is accomplished using a large square, and a drafting compass. All together there are three radius's that need to be marked, a handful of center lines, and a few lines that give the jig its shape. Exact dimensions can be found by consulting the plans or watching the embedded video above.

There is a countersinked slot that needs to be routed down the center of the jig. I use two different spiral upcut bits to do this, a 5/16" bit and a 1/4" bit. This allows the hardware that I will add to the jig later to move freely in the slot without impediments. I route these slots using my router equipped with an edge guide.

With the slots finished the shape of the jig, which is purely aesthetic, is cut using the bandsaw. You can skip this part if you would like as it does nothing to affect the function of the jig. I did it purely because I liked the way it looked and it's pretty standard for this type of jig. I smooth out the edges using my oscillating spindle sander.

With the shaping finished I can now layout for the holes needed to attach the jig to the router. I use the base plate as a template in order to get the correct placement. In hindsight It may have been a good idea to use some double stick tape and drill the holes with the base plate attached. The way I did it, which was basically freehand, leaves open more opportunities to miss drill your holes in the event your layout marks aren't exact.

I use my drill press to drill through holes with countersinks on the bottom face of the jig. These holes will accept the screws that attach the jig to the router.

The hardware used for this jig are a t-track bolt and a star knob. Before I can use the star knob however I need to cut it down a little. I'm used a grinder equipped with a cutting wheel to cut the bolt down to size.

This jig is attached to my router with the base plate removed. I use the same threaded holes used to attach the base plate to secure the jig to the router. The star knob and t-track bolt are screwed together through the body of the jig. The end of the bolt protrudes about a 1/4" beyond the bottom surface of the jig. The end of the bolt serves as the pivot point for the diameter you set when using the jig.

All that's left to do is test it out. It worked perfectly. If you made it to this web article because you were searching for ways to rout perfect circles with your router then I hope you found what you were looking for. This is a simple but handy jig to have in your workshop and I hope you make one for yourself. I'd love to hear what you think about my video and my article, so if you have a second please leave me a comment below or shoot over to my YouTube channel and leave a comment on the video tutorial that goes along with this article. While your over there if you feel like supporting what I do and my channel please subscribe. I look forward to hearing your thoughts and to your interaction in future video tutorials.

Project Plans

Router Circle Cutting Jig
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