Introduction: How to Make a Square to Circle

Another recording from the Insane Asylum.

When I cut the base for a project I've been working, i made a mistake and did not finalize the outer ring. I knew I could do it later, but had never attempted something so large. The good thing is this technique will work large and small. In this, its the method you want to learn. It doesn't depend on the tools.

When i went back to finalize the outer size, i did not have a fixed inner radial point to spin from. I still had the cut disc so i shimmed it back in, and mounted my circle cutter as featured in one of my previous projects.

I knew the shimmed piece wasn't stable enough to spin the spiral cut on. Besides i didn't want to push the spiral cut thru 1.25" of plywood thru 70 some odd inchs of wood in a single pass.

It was almost 5 hrs from picture 1 to picture 2. FYI

Tool list-

Radial Arm Saw

circle cutter


lot of patience.

Step 1: Spinning the Circle.

Using the my circle cutter, i just ran a pencil line around from a hole.

For those paying attention to the picture. You'll notice I took one of the screws out so i can get a max circle of 23.75 inches in that configuration.

Notes in pictures.

As normal, i got into the build and only occasionally remembered to photo the work for you.

Step 2: Bearing Close Up.

just in case you were wondering what the bearing is.

Step 3: Ready for Some Sawdust?

I flipped the base over, had to add some screws since the 2 pieces have never been separated since they were joined and cut. The cuts i would be making would be cut off the binding screws. I needed to add screws inside the cut ring. Otherwise if the 2 discs separated it would be hell getting them to line back up perfectly. The upper is 3/8 ply and lower is 3/4 ply. I needed mass and stability, not weight.

To do this little trick, everything you do will be cutting angles. You need to be comfortable with this.

This was the first time i've done a 45 crosscut on my RAS since i redid the top of it. *(maybe i'll do an instructable on the table top build)

I swung the saw around laid in my line and started getting busy.

Step 4: Cutting, and Cutting and More F'n Cutting.

I have no idea on how many 45 degree pulls i made on the saw today. but i finally got the rough trim down.

Now its time for sanding.

Scroll thru the pics for progress

Step 5: A Circle Is Born.

500 revolutions later.

3 sanding discs

2 tripped breakers

and one very nicely done *perfect circle.

For this part, like in the circle cutter i used my sander. I mounted the piece on the bearing my RAS and attached my large sanding drum. I spun the rough disc on the bearing against the RAS Sander and worked it all in till i could not feel a difference around the perimeter of the circle nor could get a sound when the sander was spinning telling me it was true. Later, i pulled the motor up to 45 deg and sanded a little round over on the bottom to reduce splinters.