Circle Cutting Jig for Table Saw

by Marsh

56K40114

Intro: 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

Tools

  • Table Saw
  • Sander or planer
  • Drill and Bits
  • Centerpunch
  • Countersink bit
  • Screwdriver
  • Tape measure
  • Straight edge

Materials

  • 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.

12 Comments

b1tbang3r 9 years ago

I've made one of these before to make round chair tops (seats?). Very nice job!

beantown53 9 years ago

I would make a clap dog to hold the work piece. This would greatly reduce the possibility of an accident.

Marsh 9 years ago

That's not a bad idea and if I ever have another mass production project with it, I'll add it on and update the Ible. I only made this to be able to make my checkers. We love the outdoor checkerboard.

Loetje 9 years ago

I agree with charlieCG, looks like a dangerous method to make wheels. I usually make wheels by making a rough circle on de bandsaw. Then I use the disk sander to finish the wheel. For the disk sander I have made a simple jig, to get perfect circles

noahspurrier 9 years ago

Please describe this jig for making perfect circles on a bandsaw.

Marsh 9 years ago

My bandsaw also has a 3/4" slot for a miter gauge and this sled fits right on it. It works in exactly the same way on the bandsaw as it does on the table saw. The table saw makes a better circle though because there's no flex in the blade like there is on the bandsaw.

Marsh 9 years ago

This is a well known and accepted method of cutting circles on a table saw. It dates back decades and my dad';s Monarch Radial arm saw even had a factory attachment that accomplished the exact same thing.
A table saw is a very dangerous machine, but the only way you can get cut on one is by sticking a body part into the blade. Don't do that!

charlieCG 9 years ago

I'm pretty sure no one ever turns their saw on thinking: I'm going to cut some fingers off today. But it happens regardless. I've personally had accidents doing things that seemed completely harmless. Nearly lost my left index.

Old methods that used a pivot point which was located a minimum radius from the blade to prevent kickback. The tighter the circle, the more you have to twist the blade in the workpiece. Twisting the workpiece at all is pretty much asking to get your work kicked back at you. I bet you can't find one the market for a table saw these days for liability reasons. Your method is better, it makes multiple cuts, rather than twisting. If I HAD to cut circles and all I had was a tablesaw, I would probably use a similar method.


People have come up with much better ways of cutting circles, which come out with finished edges. I have cut them safely by hand with routers with success. I made a plate that replaced the base plate on the router, which had an adjustable swing arm with a stylus point on the end. Works Great. Parts come out with smooth curves, without need for too much finish sanding. Now I use a CNC. Hands down the easiest, safest way. But not exactly accessable.

Not trying to troll, just don't want you to loose a finger.
Charlie

Marsh 9 years ago

This actually works much better than a bandsaw or jigsaw, so I would recommend it over either of those alternatives anyway.

charlieCG 9 years ago

I doubt that, having cut quite a few circles, on quite a few machines. Nice jig though, it certainly works. You need a way of clamping the workpiece to the sled after you press it onto the stylus. Then add a handle to your sled. It would make it safer, and you would likely get better results as well.


Table saws are designed for cutting straight lines, and even that, can be dangerous. Doing anything else is really dangerous. I used to love using jigs like this, and use them often. Then I saw what a table saw can do when even the smallest thing goes wrong. I have helped mop up the blood from a table saw accident, its humbling. Be extremely careful.

charlie