This is a simple circle cutting jig I built for larger jobs. It makes the job of cutting perfect circles of wood extremely easy. It can be easily adjusted to cut circles in any diameter from 15.5 inches to 78.5 inches, which will cover most project needs. You can create yours to cut larger diameters by simply making the table longer. It consists of just 2 main assemblies, the table top and the support leg. The leg is adjustable so that it can easily be adapted to your friends band saw too.
Step 1: Materials
1 Plywood (14" x 48" x 3/4")
1 Wood for miter slot (13 1/4" x 3/4" x 1/4")
2 Bolts w/ washer to mount to saw table
1 Bolt w/ washer and nut for size adjustment
1 Hinge w/ mounting wood screws
3 Wood pieces for leg (30" x 1 1/2" x 5/8")
1 Wood piece for leg spacer (6" x 1 1/2" x 5/8")
2 Roof flashing pieces for leg slip joint (1 3/4" x 1") w/ wood screws
1 Bolt (2 1/4") w/ 2 washers and 1 wing nut for leg slip joint
Step 2: Tools
Step 3: Making the Jig Table
I sized my jig to fit my band saw table. The 14" width is the same width as my band saw table.
- Cut a piece of 3/4" plywood to size, 48" x 14".
- Round over the edges using a router with a round over bit or some other method.
- Route a slot down the center of the plywood lengthwise and all the way through. This slot should be just slightly larger than the diameter of the sizing bolt, mine is 5/16" wide.
- Route a second slot down the center of the plywood lengthwise as well but only half way through. This slot should just be barely larger than the nut for the sizing bolt, mine is 1/2" wide.
Step 4: Miter Slot Wood
- Cut a piece of hardwood (I used red oak scrap) to size, 13 1/4" x 3/4" x 1/4".
- Mount the hardwood to plywood 10 inches from one of the short edges of the plywood using 3 counter sunk wood screws making sure it is parallel to that edge.
Step 5: Making the Leg
- Cut the four 1 1/2" x 5/8" pieces of wood, three 30" long, one 6" long.
- Using a 1/4" router bit cut a slot all the way through the three 30" pieces as shown.
Step 6: Assembling the Leg, Part 1
- Assemble the 6" spacer piece between two of the 30" pieces as shown.
- Put the third 30" leg piece between the two connected 30" pieces and insert the 2 1/4" bolt with washer through all 3 pieces.
- Add another washer and the wing nut to the bolt.
Step 7: Assembling the Leg, Part 2
- Using a tin snip, cut the two pieces of flashing to size (1 3/4" x 1").
- Drill two holes in each flashing for the wood screws.
- Attach the flashing to both sides of the 30" pieces at the end opposite the 6" spacer piece so that the third piece can slide between the first two pieces.
Step 8: Attaching the Leg
- Using the hinge mount the leg on the bottom of the table surface using 6 wood screws. Make sure they do not penetrate through to the other side.
Step 9: Cutting the Blade Slot
Caution! Remember to always use eye protection when you use your band saw!
At this point, you can cut the blade slot. Depending on how big your jig is you may need an extra pair of hands to do this. I did.
- Position the jig on the band saw just in front of the cutting edge of the blade with the miter slot wood in the miter slot.
- Turn on the band saw and slowly slide the wood along the miter slot into the blade cutting the slot until the band saw table top is completely covered by the jig.
- Turn off the band saw and wait for the blade to stop before proceeding.
Step 10: Securing the Jig to the Table
This step is very important! Do not skip this step! This is what I did for my table.
- The jig should still be in position from the last step, the blade half way through and the jig covering the table completely.
- Choose the locations of the holes you are going to drill. If you do not plan to tap the holes, make sure the holes will be located in a flat spot on the underside of the band saw table.
- Drill 2 holes just slightly larger than the shaft of the bolt you plan to use. Drill them all the way through the jig and the band saw table.
- Counter sink the two holes with a diameter large enough for the washers you are going to use. The counter sink must be deep enough so that the heads of the bolts will be below the surface of the jig when it is attached to the band saw.
- Remove the jig and tap the holes for the threads of the bolts you are using, if you are going to.
- Place the jig back on the band saw table with the holes aligned.
- If you tapped the holes, secure the jig to the table with just the bolts and washers.
- Otherwise, put the bolts and washers through the holes and secure with washers and nuts on the bottom.
Step 11: It's Ready to Use!!!
- All you need to do now is put the nut for the sizing bolt into the slot from the top of the jig.
- Insert the sizing bolt from the bottom and screw into the nut.
- It is now ready to use!
Step 12: How to Use the Jig
- Mount the jig to the band saw making sure to secure it with the mounting bolts.
- Adjust the length of the leg until the jig table is parallel to the band saw table.
- Slide the sizing bolt along the center slot until the space between the band saw blade and the center of the sizing bolt is equal to the radius of the circle you want to cut.
- The wood you want to make a circle of must be a little larger than diameter of the circle in both directions.
- Pick on edge to be the point where you will start cutting.
- On the surface of the wood that will not be visible, measure in from the edge and place a mark at the point equal to the radius of the circle.
- Find the center between the other two sides and place a mark.
- Drill a hole just slightly bigger than the sizing bolt PART WAY THROUGH the wood where these two marks intersect. Hint: Drill the not as deep as the bolt protrudes through the jig table. This way the weight of the wood will rest more on the bolt and it will be easier to pivot.
- You may need to cut off the corners of the wood if the distance between the corner and the circle you are going to cut is bigger that than the distance between the blade and the neck of the band saw.
- Place the wood on the jig so the starting edge is against the band saw blade and the hole you just drilled falls onto the sizing bolt.
- Make sure to wear the appropriate safety gear before using your band saw!
- Turn on the band saw and slowly turn the wood into the blade.