bandsaw circle cutting jig

[tdale51@yahoo.com]

I just made a circle cutting jig for my bandsaw and thought I'd try to post pics and somewhat of a tutorial here. Maybe someone will find it helpful. I got the original idea from a video on youtube, I think it was put out by Woodworkers Guild of America.

First I measured the width and depth of my bandsaw table (16" square in my case). Then I ripped a piece of 3/4" MDF to the depth of my table and cross cut it originally to 30". 30" proved to be too long so I cut it down to roughly 26". Then I set my tablesaw bevel at 45 degrees and my rip fence to 1" less then half the width of the piece of MDF (7" for me) and ripped it. The resulting ~7" piece got set to the side. Leaving the fence in place and the blade beveled to 45 degrees I rotated the square face of the remaining piece of MDF against the fence and flipped it so that when I ripped it again it gave me a piece ~2" (on the short side) and dovetail shaped. This should give you one dovetail shaped piece and two pieces with one beveled edge. One piece is going to be narrower than the other, that's the piece that'll receive a bandsaw kerf later. The narrowness allows the blade to slice all the way through and exit so it's not rubbing your jig and wearing things out.

Second I ripped two cleats out of scrap 3/4" plywood approximately 1 1/2" x 18".in retrospect 16" would have worked but I had an idea in my head that didn't pan out is why I went with 18". A third cleat was cut out of scrap poplar roughly 2" x 16" and set aside for now.

Now place all three pieces on your bench wide face up using something like a couple playing cards or sheets of paper between both sides of the dovetail piece and the wider boards. Align one end of the three pieces and place one of your plywood cleats across all three. Glue the cleat only to the two wider pieces (you could also screw or brad nail but I just used glue.) I don't thing these have to be dead on square just close. Next measure from the inside face of the cleat you just attached up the length of the MDF to just over (like 1/64") the width of your table and attach the second plywood cleat in the same manner as the first. After the glue has set pull out the dovetail piece and set it aside for now. Take your jig to the bandsaw and make sure the table fits between the cleats, one on the outside and one between the table and throat. I had to trim my cleats slightly with a rabbeting block plane. Once your jig fits on the saw slide it away from the blade, start the saw and then push the jig into the blade cutting all the way through the narrow side of the jig table. After I did this I noticed that if I tried I could flex the jig without too much difficulty. My solution was to cut about 6-7" off the dovetail piece and glue it in the slot on the throat side of the jig.

Now take your dovetail piece and mark a center line on one end of the narrow face and a perpendicular line 1" up from the end. The resulting crosshair is where your pivot pin will go but DO NOT drill for it yet. Slide the dovetail piece into the jig until it just barely touches the blade and position the jig so the center line of the dovetail piece even with the bottom of the blade gullets. This is the final position of the jig, clamp it the bandsaw as shown in the picture. Now using your 1" mark you made earlier as a starting point mark lines across the dovetail piece and one piece of the table at what ever increment you choose (I chose 1/2"). Use a marking knife or X-acto for this then darken the lines with a 0.5mm pencil.

Now remove the entire jig from the saw and clamp the remaining cleat underneath flush with the end of the jig but don't glue it yet. Transfer the center line from the dovetail piece to your hardwood cleat. Remove the clamps. Drill for and install a 1/4-20 threaded insert at the junction of your centerline and the width of the cleat. (I like to add a couple drops of super glue to the inserts before installing them just in case) Attach the cleat to the jig in the same manner as you did the others.

Now you can drill for and install the pivot pin in the dovetail piece (1/4" dowel or a cut off wood screw works great). You only want this peg to stick up 1/4" or so above the surface of the jig. Use a brad point bit for accuracy because if your bit walks on you it screws up all your radius lines you made earlier. Now give the entire jig a coat of your favorite finish or just wax it.

To use the jig, mount it on the bandsaw as stated previously. Determine the radius of the circle you want and slide the dovetail piece to the correct setting. Thread a 1/4"-20x1" bolt into the threaded insert until it applies pressure to the bottom of the slider. No need to go more than finger tight because any tighter will just dig into the MDF and eventually ruin it. Cut a square(ish) blank slightly oversized (1/4" or so). Find the center of the blank and drill a hole sized to fit your pivot pin with no wiggle room. Cut a notch in your blank so the bandsaw blade can fit inside to start the cut instead of outside and possibly get deflected. Place your blank on the pivot pin, fire up the saw and rotate your work piece to cut out a perfect circle of what ever size you chose.

With the dimensions of this jig I can safely and accurately cut a circle up to 15" in radius (or 30") in diameter, that is of course if I could figure out how to get a 15" piece of wood through a 14" throat.