Introduction: Circle Cutting Jig for Table Saw
Did you ever need to make a wheel or checkers for your garden checkerboard? With this easy to build circle cutting jig you can go into production in less than an hour!
Step 1: Tools and Materials Needed
- Table Saw
- Sander or planer
- Drill and Bits
- Countersink bit
- Tape measure
- Straight edge
- Piece of scrap ¾" Plywood or Melamine apx. 18" square
- Good piece of hardwood (I use red oak from old pallets)
- Some scrap wood 1"x1"x6"
- One ¼" x 2" carriage bolt
- One ¼" Washer
- One ¼" Wingnut
- Assorted drywall screws
Step 2: Measure Your Miter Gauge and Cut a Guide Bar
This jig is actually another kind of sled and will ride in the same slot as your miter gauge.
Measure the miter gauge and rip a piece of hardwood to the same width (give or take a few thousanths). Mine is ¾", which is a very common slot size. I used red oak scavenged from pallets for the hardwood. This piece should be at slightly longer than the size of your work surface (which we'll make in the next step). You'll also need another piece about 10" long.
Plane the piece down so it does not protrude above the table top. For me, 3/8" thick was just right. Use a straight edge to make sure it has been planed down enough. Sand off the sharp edges too.
Step 3: Cut the Work Surface Square
Set your rip fence to a convenient dimension and cut your work piece square. Mine was about 18", but that was just the size of the scrap I had. Leave the rip fence in place for now. You can tell the piece is square if you measure across two diagonals and they are the same. If they're not, your rip fence probably needs adjustment. It's really not that critical for this project.
Step 4: Attach the Guide Bar to the Work Surface
Set the guide bar into the slot in your table. Your rip fence should still be in place from the squaring cuts, so if you lay the work surface down against the fence, it should come right to the edge of the blade.
We left the guide bar a little longer than the work surface so we could more easily locate it underneath. This will make it easier to drill the attachment holes. Measure and mark the work surface with a line right down the center of the guide bar. Using a center punch, mark the location for four or five screw holes. If your drill bit is short enough, place it far enough into the drill chuck that it won't hit the table. If its too long for that, wrap a piece of tape around the bit to mark the appropriate depth.
Drill one hole, countersink it and install the first screw. After that drill the remaining holes, countersink them and install the remaining screws. Finally, trim the protruding guide bar ends flush with the edge of the work surface.
Step 5: Cut a Guide Slot Into the Sled
At a point about 30-40% of the length of the work surface (measured from the end closest to you). Find a suitable location for a guide slot. It should be between two of the screws in the work surface. Measure and mark that spot, then adjust the rip fence to that distance from the blade.
Measure the thickness of the guide bar. (Remember the extra 10" guide bar we made back in Step 2?) Adjust the blade height to the thickness of the guide bar. Make sure the guide bar is no more than half the thickness of the work surface. If it's too thick, plane it down some.
By taking a series of cuts across the entire length of the work surface, then moving the fence over the width of the blade, create a slot in the work surface. You want the guide bar to fit tightly into the slot. It should press in with minimal force by hand.
Step 6: Make a Stylus for the Work Piece
Drill and countersink a hole about half an inch from the end of the guide bar. Measure the thickness of the guide bar and cut a wood screw so it is 3/16" longer than that measurement. Sand or grind that extra 3/16" to a sharp point and install the screw into the guide bar.
Try the guide bar in the slot you created. If it's sticky and hard to move, apply some paste wax and it should smooth right out.
Step 7: Measure and Mark for Size
The smallest wheel I would cut with this is 4" diameter. Any smaller and your fingers are getting pretty close to the blade. Measure two inches from the blade side of the work surface and mark it. This represents the radius of the piece to be cut (your wheel). I marked mine every ½". Don't forget, every ½" of radius equals 1" of diameter of the finished product.
Step 8: Install a Clamping Dog to Hold Things in Place
Notch a piece of wood to clamp the guide bar down. Drill a hole through the work surface and the clamping dog then counterbore the work surface from the bottom. Install a carriage bolt from the bottom and the washer and wing nut on the top. This will keep the guide bar and stylus from moving when you're cutting wheels.
Step 9: Setting Up the Jig
Cut a square block and locate the center of one side. Draw a line through the center and transfer it out to one edge of the block. Slide the stylus to a point half the width of the block. Align the edge of the block with the edge of the work surface, then align the center line on the block over the center of the guide bar.
Give it a good whack with the heel of your hand and the block will be skewered onto the stylus. This stylus is all that's maintaining the center of your wheel, so don't let it move. If you're not centered on the stylus or you set the the radius too large, you'll end up with flat spots on your wheel.
Step 10: Making a Wheel
Now you're ready to cut.
First cut the corners off to make an octagon. Then cut all the corners off again to make a hexadecagon (REALLY! A 16 sided object). From here you can nudge the block up to the blade in small bites and rotate it to round it out. You can even add embellishments by adjusting the blade height.
Makes a perfect checker if you happen to have a garden checker board like this one.
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