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Thread: How to cut 24" circles out of 1/2" thick maple plywood in LARGE quantities?

  1. #61
    Join Date
    Mar 2003
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    The first thing that came to mind for me (other than a CNC router) is a simple jig. Use a suction cup meant for the glass/glazing industry, with a pivoting beam attached to a good router with a 2-flute carbide 1/4" bit. Suction the jig to the face of the plywood, turn the router on and rotate the beam-mounted router around the center until you get a circle. No center hole, clean cut, and you can fix the beam to any length you want to vary the diameter of the circle. A good bit should be able to cut through 1/2" plywood in one pass, or just adjust once and make a second pass.
    Jon Endres
    Killing Trees Since 1983

  2. #62
    Join Date
    Nov 2016
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    Richmond, VA
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    Here's one approach: break down the large sheets into 24" squares; then cut the circle on the bandsaw using a simple circle cutting jig (perhaps even in multiples); then sand using a jig on a disc sander. Most of the kerf loss will be on breaking down the sheet. There should be very little kerf loss from the bandsaw. If you don't have a disc sander, you could buy a sanding disc for your table saw like this:

    https://www.amazon.com/CMT-299-111-0...pcontext&psc=1

    The cool thing about woodworking is there are so many ways to get to the same place.

  3. #63
    Join Date
    Nov 2016
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    Atlanta
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    Anther idea would be build a dedicated machine. Gang mount 8 routers to a platform that will plunge down then move the platform following a template. You could cut all 8 out of your sheet at once. Gang cutting and eliminating the need to precut squares. is what is going to get you the productivity you want. If the edge finish as routed isnít good enough then edge sand them. With a custom clamping setup (think of a big c-clamp with pads that can rotate) mounted to a table in front of a belt sander you could easily sand 8 at a time. With a guide and some stops controlling how much you can feed into the sander you could have extremely repeatable diameters.

    Bet you could do this for a lot less than a 4x8 cnc.

  4. #64
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    Apr 2018
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    Cambridge Vermont
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    Interesting thread. I'm not sure if it's been mentioned but to cut them on a bandsaw you will need to break the sheet down to fit the throat of the bandsaw. I have a simple jig I made out of steel (but could be made from wood) to cut round blanks for turning. It has a pin (1/4" bolt that has the head cut off). I simply drill a hole just deep enough for the pin to sit into the blank. Mine is adjustable for any size blank. If all you were doing was 2 sizes you could easily make up a jig that you could clamp to your bandsaw that has to holes for the pin, one for each size. You said you could live with a hole in the back so with a forstner bit you could drill half way through to make the pivot hole. With a good bandsaw and a fine tooth blade you shouldn't have much cleaning up to do. I've made a few round circles with my jig out of 1/4 lauan and they came out perfect and it really came down to how fast I could rotate the wood as to cutting speed. But you would need to make the square blanks, mark the center of the blank, and drill the hole. Plus stacking them might work fine but since only the bottom sheet would be secured to the jig you would want a way to secure the other sheets to the bottom one.

    However, my advice is to spend as much money on a tool as possible. Some of us on tighter budgets like to live through the spending of other people's money. All kidding aside I would pick the solution that could offer the most options to do other things you may do in the future.

  5. #65
    Six would be correct.

  6. #66
    Bandsaw using a circle jig. Pattern rout to finish.

    Mike

  7. #67
    You can, in fact, get six pieces using a CNC.

    Itís a 2í diameter circle, not a square, so there are no corners. The software will nest the six pieces off axis from each other in two rows of three pieces.

  8. #68
    Yes, this is the quickest way.

    Overcut the circle a hair bigger than twice the laser burn thickness, then use a shaper or hand held router with a pattern cutting bit. It will quickly shave off the burn, and you shouldnít require any edge sanding.

  9. #69
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    Just a thought....
    How about cutting a bit oversize and make a jig to sand it smooth?

  10. #70
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    I would do it with a jig on the band saw. I would make a plywood table with post to be the center and put plywood blanks on the post and rotate the whole thing to make the circles. The post could be a nail.

  11. #71
    Join Date
    Jan 2008
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    Fastest, by far (under a minute per stack), with the least waste, is a bandsaw with a circle-cutting jig. You can stack blanks with double-stick carpet tape. A tiny center-hole in the bottom blank or a thin hardened Masonite template (my choice). You can also use double-sided tape to attach a center pin (no hole).

    CNC has the advantage of no babysitting if you have a big-enough bed (4' x 4' or 4' x 8').

    BTW, use lightweight carpet tape (not heavy duty), and use it sparingly. Pay attention to bandsaw blade tension to assure a vertical cut through your stack.

  12. #72
    Quote Originally Posted by Byron Lu View Post
    Isn't it true that a CNC router will be slower and have to go multiple passes in order to cut a 1/2" thick plywood? In addition, you can only cut one piece (no stacking) each time and you have to setup a jig to hold the piece too. I guess it would be slower than my current laser cutter.
    You can cut them on a CNC, but yes, even if the CNC can cut in one pass, it's probably slower than a bandsaw jig.
    Another problem with CNC is that a circle is the most difficult thing to cut accurately. It is much harder than just cutting out a square. Of course, it is possible, but a lot of time spent on backlash adjustment and other tuning.

    Unless you want to buy a CNC for another task, a bandsaw is much faster and easier, especially at the amount you have to do.

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