Cutting circles freehand with a jigsaw or band saw is not easy and never precise.
A friend of mine called today and told me she needed a 32” round piece of plywood to temporarily protect a glass table. I thought this would be a good opportunity to discuss making a circle cutting band saw jig.
The band-saw shown here is a JET 14 Inch Band Saw Model 708115K. Read the review on this saw here.
There are numerous woodworking projects, such as round table tops toy wheels, lids or archways that call for precise, rounded cuts, the kind that cannot be consistently cut by hand. Realistically a band-saw or a router is best to do these cuts.
I’ve cut circles with circle radius ranging from a few inches to a couple of feet. The only limit is the distance from the fence to the saw blade.
Making A Circle Cutting Band Saw Jig:
A circle cutting band saw jig can cut perfect circles and the jig itself can be made with some scrap plywood and 30 minutes of your time.
I used an old shelf and some scrap ¾-in. plywood to make my jig. It is essentially an extension table that allows me to install a finish nail [pin] in the top.
First order of business was send the jig through the blade to create the saw kerf, then shut off the saw when the extension table reaches the edge of the saw table, I over cut about 1/8 in. to keep the saw blade away from the jig.
To mark a square line and run it through the band saw until my table extension was flush wit the band saw table.
The old shelf I was using had a 1×2 edge nosing applied and I used that nosing to flush out the shelf with the edge of the band saw table.
My table extension has three scrap pieces of plywood that are installed against the sides of the band saw table as stability supports. One of these scrap supports also receives a screw through the band saw table and into the support to keep the table from lifting. This eliminates the need for a clamp.
The supports function to index the table with the blade but also to hold everything steady while you turn the actual circle stock through the blade.
Once everything the extension table was attached to the saw I
leveled the table and attached an auxiliary ply wood leg to the out feed to support the table and keep it from sagging under the circle stock weight. Two screws hold this leg in place.
Measuring your circle prior to cutting:
I then squared a line from the blade down the extension table and is that line to make my measurements on. My friend wanted a 32” radius cut on her plywood so I measured 16” from the band saw blade, made a mark and then installed a 6 penny finish nail.
On the plywood I cut it to a 32” x 32” square and then measured diagonally from the corners to determine the center. Once I had the center marked I drilled an 1/8-in. hole through the center.
Cutting your circle:
Thinner blades work best with the circle cutting band saw jig in fact a ¼-in. blade is perfect. Placing the circle stock plywood over the extension table nail and make sure the circle stock is flat to the table.
Turn on the saw and slowly turn the wood though the blade to make a circle.
Cutting different size circles:
This circle cutting band saw jig is ideal for cutting circles anywhere from 2″ to 48″ in diameter but I actually have a much smaller jig for small circles that does not extend nearly as far and does not need an extension leg to support the table.
Avoiding the center hole on your stock:
Some projects like furniture and table top pieces require you to cut precise circular shapes while avoiding the center hole in the stock. To do this on the circle cutting band saw jig you need to use two sided tape and attach your stock to a sacrificial surface. The sacrificial surface can then be mounted to the jig extension table pin.