Woodworking Stack Exchange is a question and answer site for professional and amateur woodworkers. It only takes a minute to sign up.
Sign up to join this community
How can I cut a large (3.5' - 4' in diameter) circle out of a 4x8 sheet of plywood. The preferred method would be one that doesn't leave any holes/marks in the circle's plywood surface. It needs to be as near perfect as possible (shape/edges of the circle). The circle cutout will be used as a table top.
The tools that I have at my disposal are: Router, Dremel, circular saw, 10" table saw, 14" band saw, 10" drill press, jigsaw, and a lathe.
How can I cut a large circle out of a 4x8 sheet of plywood?
You sound like the perfect candidate for a router circle jig. The one linked is available at Rockler, but they are easy enough to make yourself out of plywood.
The preferred method would be one that doesn't leave any holes/marks in the plywood surface.
The one pictured uses a pin to keep the jig centered. This will leave a small hole in the plywood that you could either keep on the bottom side (assuming it doesn't go entirely through) or find a way to cover up.
Otherwise, you should be able to find a way to affix the circle template to the plywood in a non-marring way, such as using double-sided carpet tape.
There are other means to make a large circle, as identified in this related Question. However, in my opinion, none will leave as nice of an edge finish as the router.
You can cut a perfect circle top using your table saw.
To do this, you will need a jig (a large sheet of plywood with a pin on which the board being cut spins).
Cut off corners (on the work piece) to remove large amounts of excess material. The first set of cuts take a square piece to an octagon. Then cut off more corners.
Using the jig, you can slowly cut off the excess by spinning the work piece.
Here is one example I found showing this technique: Cutting large circles on the table saw
If you need to have both sides of the work piece without holes, you can attach it to a sacrificial board using double sided tape.
Another option if you want to buy a tool for your Band saw, there are circle cutting jigs. The Carter one can cut circles over 4' in diameter. I have one of these, though I've only used it a couple times. For flat stock it works pretty good, I bought it to cut bowl blanks round. You need to have your band saw tuned up well to get best results.
[
[
Pick one according to skill level.
Hook it up to your lathe after cutting it down to an octagon or hexadecagon, (squares are unruly,) and use a wide lathe bit to trim down to a penciled circle. Sand to perfect straight edges. Only try this, though, if you are good at lathing.
Also, you can put a nail in the middle, hook up a hand- moved power saw to it with a string as you would with drawing a circle, and ever so carefully pull it around the string into a perfect circle. You could also use a little wood and a nail or two to make a compass, which does the same thing. You can pull this with a little less skill using a router.
For a little money, you can put it on a device that spins it into a saw blade until it's perfectly circular with a pin. If you're willing to spend any money, you can buy a circle cutting jig or similar device for downwards of 400$. If needed, sacrifice a small piece of wood that holds the pin and is duct-taped on. This can be a piece you cut off to start.
If you absolutely want no marks on either side of your workpiece, use a router circle jig as above and make a template. Attach it to your workpiece with double-sided tape and use a pattern bit. Cut close to the line with a jig saw and finish with the pattern bit.
