Introduction: How to Build a Circle Cutting Jig for Your Router

In this Instructable I will demonstrate how I make quick and easy circle cutting jigs for my trim router.

In some cases a jigsaw will do the job when you need to cut out a circle for a project but if you need to cutout a perfect circle that will be visible, a circle jig is your best bet. Well, unless you have a CNC machine, in which case this tutorial is not for you.

If you are on a cell phone the embedded video feature doesn't usually work. Not a problem, You can watch the video right here instead:

WATCH VIDEO HERE

The materials and tools I used for this project are as follows:

Router

Screw Driver

Router Cutting Bit

Table Saw

Cordless Drill

Drill Bits

Forstner Bits

Countersink Bits

Tape Measure

Speed Square

Combination Square

Dowel Pins

Step 1: Remove Router Plate

Not all routers are the same but I am pretty sure that almost all of them will have a removable base plate. I chose to use my small trim router just because it is compact and light but you could use any type of router for this.

Remove the base plate from the bottom of your router and set it aside. This will be used as a template to mark where the mounting holes will be drilled into your jig.

I wanted to set up my jig to be able to cut a circle big enough to mount a 6 1/2" speaker so I was able to keep my jig pretty small. I also chose to use 1/4" hardboard because it is cheap, thin, and more durable than paper or cardboard.

I used my table saw to cut a piece of hardboard that is slightly longer than the size of the circle I plan to cut and wide enough to mount my router.

Step 2: Mark and Drill

Once you have your piece of hardwood cut to size it is time to make a few measurements and drill some holes. Grab the base plate that you removed from your router and place it near the edge and mark out the screw locations with a pencil or a center punch.

I used a 1/8" drill bit to drill out the 4 holes for the mounting screws then a 3/8" forstner drill bit to countersink the screws.

Next drill a 1/2" hole in the center of the 4 screw holes to allow your router cutting bit to pass through.

Step 3: Mount Jig and Drill Pivot Hole

Use the screws that you removed when removing the router base plate to mount the jig to your router. Once mounted, lower your router so that the cutting bit protrudes just slightly past the surface of the jig. Once you have determined the radius of the circle you want to cut, measure from the outside of your cutting bit to the center of your pivot point. This distance should be the radius of the desired circle. Once marked, use what ever size drill bit to match the size of dowel pins you have, and drill your pivot hole.

Step 4: Circle Cutting Time!

If you have made it to this step your jig is now complete and ready to test out.

To use this jig, all you have to do is:

Measure and determine where on your project you want to cut out the circle. once you figure that out, you also have to find where the center of the circle shall be. If you are using 3/8" dowel pins then you need to use a 3/8" drill bit to drill your pivot hole.

Once you got your project all measured out and drilled, simply place your jig over your project and insert the dowel pin through both the jig and the hole you drilled for a pivot point.

Now comes the fun part, cutting out your circle with ease. Once you have your pivot dowel in, you simply turn your router on and watch your jig do all the work.

BAM!!!

Perfect circles every single time

Step 5: Circle Cutting

And there you have it folks, a quick and simple build that will save you a lot of time and provide you with clean and accurate circles over and over again.

Please view all of the detailed photos, and watch the embedded video.


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Comments

author
IanC113 (author)2016-12-22

Cut the wood plate down the center where the dowel fits in (long oval hole). So you have one long continuous hole the dowel will fit in. Cut the dowel top off and add a screw and washer on top of the dowel. So you can loosen and tighten the dowel. That way you can adjust the jig to size just by loosening the dowel to the radius of the circle you want.

I hope you get that.

author
LarryW3 (author)2016-11-02

Excellent!! You were, I think, searching for "the outer diameter of the hole". A quick note: If you are cutting discs/wheels, etc., then the pivot dowel would be measured from the other side of the cutting blade so that the outer diameter of the removed piece is the diameter of the wheel/disc you are cutting. Nice, clean and DIY simple jig!!

author
fleabay (author)2016-11-01

Excellent idea with brilliant clear & concise demonstration - thanks heaps.

author
arvevans (author)2016-11-01

By adding an adjustable cleat (slotted mounting hole(s)) across the bottom this can become an edge-guide for shaping the edges of material with straight or shaped router bits.

author
nonobadog (author)2016-11-01

You probably want to be careful right at the end of the cut when the center part including your pivot hole becomes free. It seems it would be pretty easy to mess up the edge of the circle at that point.

author
Anirudh Ralhan (author)2016-10-31

Nice...

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Bio: I am a Building Automation Engineer at a major University in California. My favorite people in the world are my wife Bouavon, and my two ... More »
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