Cutting Circles

[Amiers]

Preferred Method to cutting smaller perfect circles out of plywood or 1x material. Circles 6 to 10 inches. 30' rule doesn't apply.

I adapted this method. To make it as safe as I could I took a 2x4 and dropped the bolt through that and the piece I was cutting so I had something more to hold on to and keep my hands away from the blade.

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What is yours?

 

[DRU]

I like to use my router and piece of lauan. Rip the Lauan down to the width of the router base. Mount the router to one end (making sure it's centered) and plunge the router blade through the lauan to locate the blade on the other side. Then I like to draw a line tangent to either side of the circle and perpendicular to the edges of the lauan (one line for inside circle cuts, and one for outside circle cuts). Then I cut a notch on each line big enough for my tape measure end to fit, which makes finding the radius quite easy. Measure the radius, draw a perpendicular line and find the center, then screw it down to the center and swing it around. I usually use a 1/4" bit and make multiple passes. You can't get too close, but I think I've done 6-10" radii before. If I need anything smaller I just bandsaw it out. Once the piece of lauan gets too many holes, I cut it up for other things and make a new one. Cheap and simple, but works beautifully.

I personally don't like using circular blades for cutting circles. Although I have heard a funny story of a guy cutting a 30' radius circle out of sheets of plywood using a wormdrive circular saw and some rope.

 

[ruinexplorer]

I personally don't like this method after a shop foreman was demonstrating it and the saw had kickback. The piece began spinning wildly around and even though he turned off the saw, the center whole broke and the remains went flying. No one was injured other than the foreman who had the piece hit him initially with the kickback (left a nasty bruise on his gut). After that, we only ever used the router method.

 

[Colin]

I would absolutely never use a table saw like that, and someone is likely to get hurt trying, compared to a number of other options that people employ frequently and safely. If you have a band saw, you can pin your radius to a MDF table and spin perfect circles quickly and very safely. If no band saw, then a router. You can also make a compass with a jigsaw on the end (for bigger circles anyway). Some jigsaw feet come with holes that work for attaching to a length of 1x or whatever, and if yours doesn't then you can drill some. Jigsaw doesn't match the precision of band saw or router, but better than freehand if you are less than excellent at following a line.

 

[Colin]

I personally don't like using circular blades for cutting circles. Although I have heard a funny story of a guy cutting a 30' radius circle out of sheets of plywood using a wormdrive circular saw and some rope.

Yes worm drive circ saws can cut curves. Only worm drive. Not sure about the rope... Seems like it would increase chances of losing control. I would rather use my steady hand only.

 

[Amiers]

This wasn't my first choice of action. I did try with a jig saw but the results just were not what i was looking for. We don't own a band saw and to be honest the band saws at the stores just look to flimsy. So I went with the table saw method. Yes there is some resistance. However if you raise the blade in small increments everything cuts pretty easy.

 

[Colin]

Another option is to find a laser cutting shop. There are several near me, not sure about your area. A couple months ago, my wife had one cut some shapes that she drew in Illustrator, and she actually had to insist they take a little money. Once the huge expense of the cutter is out of the way it doesn't cost them much to run it. A school around you might have a laser cutter bought by a grant and sitting unused (thus pissing off the granting institution). You might pay cost of material only. Lasers are about as accurate as it gets, and you can send them any vector based file to cut from. Super convenient.

 

[bobgaggle]

I don't know about this, I've seen it done a lot, even saw a guy make a bowl on a TS, turned the inside and outside radii with a special jig. I'm not sure how this is OP's 'preferred' method of cutting circles. The table saw should be your last choice for cutting arcs, given how its designed to cut straight. And for thinner material as mentioned in the original post, the band saw with jig is the way to go. Even the cheap ones at home depot are fine for this application.

I made this one...

The pin is mounted in a dovetailed rail (only an 1/8" hole needed in the work piece, better than a giant bolt). The knob at the bottom locks the rail in place at whatever radius, measured from the blade. I had a scale mounted on the jig so I wouldn't have to break out the tape measure, but it ended up being more accurate to measure from the blade. There's a rail on the bottom to fit into the saw's miter gauge slot. And we had some left over faux burl laminate so I glued that on top to keep things slippery. The only problem is when the jig isn't set at zero the burl pattern doesn't match up anymore

 

[BillConnerFASTC]

Band saw and table. Built a gazebo (scenery) with a 8' radius - used lots of scrap ply - cut pieces of varying lengths - basically 8' and 7' for a 1' wide band - and simply stacked them. Two pins on a sliding table cut ends of pieces perfectly square on radius. Don't feel at all safe with the table saw and tight radius.

 

[gafftapegreenia]

Since we have a CNC router, that's my preferred method.