The ability to cut a circle in wood will open up a wide range of shop opportunities and you’ll be able to make more projects. With a router circle jig, you’ll be able to easily cut a perfect circle.
How often do you need to cut a circle? In my case more and more often. For this project one of my requirements was to make a circle router jig that would be simple, easily adjustable yet elaborate. I wanted to be able to use this jig over and over again. I could have gone with a more rudimentary build but I wanted this one to last. So I put in a bit of extra effort.
Another requirement was to have the base plate as thin as possible so that the remaining bit length was still sufficient to be used, but at the same time to keep the base solid.
The overall dimensions of this circle jig are 51,5 x 10,3 cm, which will allow you to cut a circle with a maximum diameter of 64 cm. The smallest circle that you can cut will have a diameter of 2 cm.
This is an intermediate woodworking project requiring a trim router and other basic tools. You can check out the woodworking jigs I used to build it (see at the bottom of this post), though they are not necessary.
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Table of Contents
- The material you will need
- Router Circle Cutting Jig Plans
- General Questions
- How difficult it is to make a router circle jig?
- What router bit do you use to make a circle?
- How do you cut a perfect circle with a router?
- How to Make a Router Circle Jig
- How to Cut a Circle with a Router Circle Jig
- Router Circle Jig Video
- Woodworking Jigs Used
*Safety is your responsibility. Make sure you know what you’re doing and take all necessary safety precautions while working with power tools. Safety comes first!
Always be cautious and careful when using any power tool.
Material needed to make the Router Circle Jig
Router Circle Jig:
1x MDF desk (51,5 x 10,3 x 0,5 cm) – final dimension) – start with (51,5 x 20)
1x Plywood desk (44,5 x 10,3 x 0,65 cm) – final dimension) – start with (44,5 x 20)
1x Plywood desk (10 x 1,5 x 0,65 cm)
1x M6 Bolt – 2,5 cm
Wood Knob, T nut
Brass rod ø4mm, 1cm
7x Countersunk Wood Screws – 1 cm
Router bit – ø6mm Straight Router Bit
Wood Glue, Epoxy
Self Adhesive measuring tape
16 mm straight router bit
How difficult it is to make a router circle jig and what do I need?
If you want to make this specific circle router jig then this is not the easiest project and I wouldn’t recommend it to beginners. You would be able to find other more rudimentary builds working in a similar way that would be more suitable for beginners.
But if you are looking for a build where you can adjust the circle jig as necessary and set the circle diameter precisely as needed, then you might consider building this one even if it would be a bit more demanding. This is an intermediate woodworking project.
Apart from the listed material you will need a router and potentially a jigsaw a hand saw or any other power tool to make the cuts.
What router bit do you use to make a circle?
To cut a circle in wood you can use a straight bit – a double flute straight router bit. If you will slowly and gradually trim the individual layers you will get good results for most of the materials. This way you will not burn the bit and the cuts will be clean.
Nevertheless, you can use a more specialized router bit like the spiral bit. The cuts will be cleaner since there is a more constant contact when routing and there is only a small point of contact between the bit and the cut piece – that is a huge advantage in comparison to straight bits. A spiral bit will also pull up the chips from the cut and will provide nice chip clearance. Look for a carbide spiral up-cut router bit.
But take into account that these benefits are reflected in the price of the bit – more expensive but better 😉.
How do you cut a perfect circle with a router?
Mount the router base on the circle jig and tighten it down with screws. Set the circle diameter by adjusting the pivoting point in the slot and locking it down with a wing nut or a wooden knob. Insert the pivot point in the center of the circle and make a cut by slowly rotating the circle router jig and the router.
For more details take a look at the section – how to cut a circle with a router circle jig.
The circle jig consists of 2 main parts:
- Base unit – the base unit is made out of MDF and plywood. The thinner the base the better so that a sufficient remaining length of the router bit can be used. Nevertheless, the base unit still needs to be thick enough to withstand some pressure. The router is attached to the base unit.
- Pivoting pin and the adjustable runner. The pivoting pin is made of a brass rod and the runner is made of plywood. They serve for setting up the diameter of the circle and fixing the router jig while making the cut.
NOTE: All router bases have different sizes. Take into account the size of your router base so it fits perfectly for your jig. Adjust the dimensions of your jig so the router fits perfectly.
How to Make a Router Circle Jig
Step 1: Make the Circle Router Jig Base Unit
Start by cutting the MDF and plywood desks for the base. I cut 2 larger pieces around 20 cm in width each that will be cut to size in a later step. These 2 desks will create a t-track for the pivoting pin.
The thickness of the MDF piece is 0,5 cm, which makes the piece strong enough, but at the same time, it does not take much from the length of the router bit.
TIP: The reason why I am using an MDF as a base piece is that it slides quite nicely on other materials. You could also use an acrylic sheet instead but that would be more costly.
1) Cut the Base Desks
Place the router (with the footplate) on the edge of the MDF desk and mark the width of the router base. Make a mark on each side of the desk.
Cut a groove along the desk leaving 4,5 cm from each of the sides using a ø16mm router bit. The groove will be cut right in the middle of the desk. I used a spirit level as a guide rail to make a straight cut but you can use any other straight edge guide.
Measure the width of the measuring tape and cut a shallow groove right next to the first one. The depth of the slot should be just enough to sink the tape.
This is the bottom of the circle jig which will be facing down.
Follow the same process with the second base piece (plywood piece). Use a ø6mm router bit to cut the groove. Leave 5cm on one side and 4 on the other.
2) Fix the Desks Together
To cut out the desired shape temporarily fix both pieces of the circle router jig together using double-sided tape.
Draw the design on the base piece and cut off the wood excess. One side of the jig is wider. That’s where the trim router will be attached to it. To make a straight cut I used this Circular Saw Guide Track
Separate the pieces again and cut off the extra wood from the plywood piece so that the router nicely fits in. (The router will be attached to the MDF desk only).
3) Attach the Router to the Base
NOTE: Before moving forward make sure the router is turned off, the cable unplugged, or the battery removed.
Remove the footplate from the router by unscrewing the screws from the footplate.
Trace the holes from the footplate onto the MDF desk.
Drill the holes with a ø6mm router bit and a ø10mm Forstner bit to countersink the holes for the screws to make them flush with the bottom of the base piece.
To attach the router to the base plate I am using the same screws that I unscrewed from the footplate.
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Step 2: Make the Pivoting Pin for the Circle Jig
1) Build the Pivoting Pin
The next step is to make the pivoting pin and the slider. The pivot pin is a ø4mm brass pin and is 1cm long.
First, cut the slider. It is 10 cm long, and 1,5 cm wide and the thickness is equal to the thickness of the MDF desk. Since the MDF is 0,5 cm thick and the slider 0,65 I sanded the slider down until both pieces were of the same thickness.
TIP: Round the corners of the slider so it moves easier in the slot.
Drill a ø4,2mm hole for the brass pin on one side of the slider and a ø6mm hole for the bolt on the other side.
NOTE: The distance of the holes from the edge of the slider will determine the minimum diameter of a circle you will be able to cut.
In my case, it is 1cm for the pin and 2cm for the bolt.
Before gluing the pin and the bolt make sure the bolt’s head is flush with the bottom. You can either carve a hexagon for the head or drill a larger hole with a Forstner bit and use epoxy.
I used the latter since the thickness of the slider is only 0,5 cm and you need to take into account the head’s thickness. Also, if you have a grinder you can grind down the bolt’s head and make it narrower. That will help a lot.
Once finished with pivoting pin and while waiting until the epoxy hardens you can fix the 2 base pieces of the router circle jig together.
Glue them together and additionally, you can fix them with screws.
2) Make a Wooden Knob
I am using a wooden knob to fix the slider in position but you could also use a wing nut as well.
NOTE: Use a Star Knob Jig to make wooden knobs. If you have a drill press this is a handy jig that allows you to easily and repetitively make shop knobs.
If you don’t have the option then you can make a knob by cutting a circle with a hand drill.
How to make a wooden knob with a hand drill:
- Mark the circumference of a knob. I used a 38mm saw hole for that.
- Drill 10mm holes every 60 degrees. That will create a six-pointed star knob.
- Drill a 6mm hole in the center for the bolt and a 20mm hole with a Forstner bit just enough deep for the T-nut to be flush with the knob.
- Cut out the knobs with a saw hole.
Now assemble all the pieces of the circle-cutting jig together.
Step 3: Assemble the Router Circle Jig
Mount the slider in the groove and secure it with a knob.
Fix the router to the circle jig base with screws.
Mount the router bit and and stick the self-adhesive measuring tape.
NOTE: The position of the measuring tape – before/after the router bit will determine whether you would be working with the outer or inner diameter of the circle. Take that into account when setting the circle diameter.
And the router jig is finished.
How To Cut a Circle with a Router Circle Jig
The steps below describe how to set up and use a picture frame clamp. To better understand how to set up and use the jig, refer to the included video.
How to use a router circle jig
- Use an MDF or Plywood desk as base
- Lay the board on the desk and screw it in place or use double-sided tape
- Drill a hole in the board for the pivoting pin
- Set the circle diameter
- Mount the router circle jig and start cutting
For the cuts, I recommend a 6mm straight bit.
TIP: Whatever material you are cutting, I recommend making multiple passes. After each pass clean the groove from the sawdust adjust the router bit and continue cutting. Cut off around 3 mm of wood each pass. (Take into account the type of material you are cutting)
Repeat the process until you’ve cut completely through.
I have been using this router jig for some time now and I am really happy with how it turned out. I have already used it on multiple projects with great success. It was fairly easy to build though the pivoting pin turned out into a fun challenge 😉.
So… If you want to have a nice addition to your router jig gear go for it.
How to improve a router circle cutting jig
While using this circle jig I came up with an enhancer that would make it even easier to use. Generally, it is quite inconvenient that you have to screw the router base to the jig whenever you want to use it. If you’re cutting circles once in a while I guess it’s okay, but if you’re using it every other day then it gets quite tiring.
- Screw-less attachment. Use a quick-fix attachment to fix the router on the cutting base by placing the router between bearings. This not only solves the problem of attachment but also improves the work with cable routers.
Also, this circle jig uses a pivoting pin which leaves a hole in the circle once you are finished. It would be also good to have the possibility to cut a circle without leaving any marks on the surface.
Router Jig Circle Video Tutorial
Watch the video below for a step-by-step guide on how to make a router circle cutting jig.
RELATED: Also, check out these other Router Jigs and make a nice addition to your workshop.