Why make a circle jig? Why to make wooden circles of course! Why do you need wooden circles you ask? Here are some fun things you can make with circles (and arcs!):

1. Wheels for wooden kids toys

2. Hula hoops -> https://www.instructables.com/id/How-to-Make-a-Wo...

3. Table tops

4. and much more!

There are many circle jigs which you can buy, but they are pretty expensive and can be limited in ways which restrict what you can do with them. Using this method, you can make a jig to suit your exact needs.

Please be careful when using a router! It is a powerful tool and mistakes can happen fast. Watch where you are cutting, and lock down your work piece to be safe.

Let's have some fun! :)

Step 1: Step 1 - Tools and Materials

Tools:

A plunge router - I use a Makita Plunge router and you'll need this for the jig and for making the jig
A 4mm router bit and a 8mm router bit
A drill for making the necessary holes
A drill bit the size of your selected screws (see below) and a countersink
Straight edge
Carpenter's Pencil (these are great, you'll never lose them!!)
A good set of Bar Clamps

Materials:

Two machine screws to affix your jig to your router (it may be more according to your router's base
A washer and a long bolt with a nut. I used an m6 bolt which was 3cm long.
A piece of wood that is no thicker than 1cm. The width and length of the wood is up to you and can be defined by your exact needs. Mine was 8cm wide and about 70cm long.
An extra scrap of wood for the knob, or a plastic knob with a hole for the m6 screw.

Step 2: Step 2 - Let's Get Started by Routing Out the Slide

The first thing I did was route out the slide where the knob will go. This will be done with a step that the nut can be recessed into, so be aware that you are making two cuts, one with the 4mm router bit which goes all the way through and a second shallow cut which goes only 3mm deep.

Start with your straight edge and mark a line down the center.

Route out the first line with the 4mm bit. This is the track that the bolt will slide in. Follow carefully with the 8mm bit and route out a recess for the nut to slide in.

Step 3: Step 3 - Let's Make the Knob

I used a scrap of for this knob, but you can use whatever you like. There are plastic knobs which can be purchased to make this look a bit more professional, but it really isn't necessary. If you want you can get some here: https://amzn.to/2OCRDco

The end of the knob needs to be ground to a point. This is what the jig will swivel on. You can use a file or a grinder. I use a grinder whenever I can because they are fun :) I did finish up with a file to get a nice consistent point though.

Step 4: Step 4 - Drill Holes to Fit Your Router

Last but not least you'll need to drill some holes to attach the base of your router to the jig. It can be a bit tricky to map the exact center of the holes to your jig. What I found works well is to drill one hole exactly and the second hole find approximately. Then instead of one hole, make a slot by drilling two holes very closely. This will give you enough wiggle room to fit your router snugly. I made sure to go back after drilling my holes and countersink the holes so that the jig will sit flush to the work piece.

The center hole can be drilled out or you can simply plunge your router through (carefully!) after you've affixed it to the jig. I opted to drill the hole out because I wanted it to be a bit bigger than my router bit.

Step 5: Step 5 - Route Out a Circle!

To use the circle jig:

Find the center of your work piece
Drill a small pilot hole and fit the point of the jig in it.
Open the knob on the jig and set your radius by sliding it open or closed to your desired length. Remember that you're routing out a groove and that you must take the width of the bit into account if you need an exact size!
Lock down the knob to set your radius.
Start routing. Make sure to go in a clockwise direction only! If you go in a counter-clockwise direction the knob will loosen and your carefully set radius will get lost!
Go slowly when routing. Start with light passes until you get a feel for it. Never go more than 3mm in depth. There's no reason to hurry. If you take your time, it will go better!