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

[Byron Lu]

I need to cut 50 to 100 round circles out of plywood in batch every month. Right now I cut with laser machine but they always have brown edges I have to sand off. Speed wise about cutting one circle for 3 minutes with laser.

So what would be the fastest way to cut such circles in bulk? I read about some ways: routers, jig saws, band saws, table saws, etc. But I am not sure about how fast each method cut large circles out of 1/2" plywood as I do not have experience with these methods. Can anyone with experiences advice which way is the fastest in cut circles in bulk?

Thanks in advance.

[Matthew Curtis]

I would stack them up and cut a pile of them on the bandsaw with a circle cutting jig.

[Malcolm Schweizer]

If you go to my post “I now get paid to play with tools...” I’m building 56 arched doors. I cut the arch on the bandsaw with a simple jig- plywood with a screw at the pivot point. It helps to have a massive 3-phase bandsaw with insane inertia that plows through anything. It takes literally less than a minute per arch. If it were me, I would stack them up 3 or 4 high and make multiple circles at one time.

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[johnny means]

What are some other parameters? Can the have a hole on the middle? How precise do they need to be? How clean an edge do you need?

[lowell holmes]

If you do not have a good bandsaw, it is time to go shopping.

[Brian W Evans]

I don't have one (yet), but wouldn't this be a perfect job for a CNC router?

[Steve Jenkins]

I don't have one (yet), but wouldn't this be a perfect job for a CNC router?
Yes it would. If you need a full 24” you wil only get 3 pieces from 4x8 sheet of ply. You might look at pricing 5x5 Baltic birch

[Bill Space]

Yes it would. If you need a full 24” you wil only get 3 pieces from 4x8 sheet of ply. You might look at pricing 5x5 Baltic birch

I could be wrong, but my gut is telling me a 4x8 sheet should be good for six pieces 24” in diameter.

[Byron Lu]

WOW thanks so much for the replies. It seems the consensus is to use a bandsaw to cut 3-4 pieces each time. Sounds like the most efficient way. CNC routers will be quite bit slower as I understand.

Other parameters: I need the edge to be clean and smooth. A tiny hole on the back of the circle will be okay but not on the face side. Would be nice if no hole at all.

I can usually cut a 4x8 into 8 pieces of 24" rounds (well 23.5" each instead). The laser edges are very smooth but with the brown burning edges. Can a band saw cut it with a smooth edge?

I can only use a single phase bandsaw if this is the direction to go as it will stay in my garage. Any recommendations on what type/brand/config of the bandsaw suitable for my purpose?

Again thanks so much for your help!

[Byron Lu]

Sorry for some reason I am never able to open the image attachment in this forum. Is that a jig photo? can you post somewhere or give a link so I can see how to make the jig? THANKS.


If you go to my post “I now get paid to play with tools...” I’m building 56 arched doors. I cut the arch on the bandsaw with a simple jig- plywood with a screw at the pivot point. It helps to have a massive 3-phase bandsaw with insane inertia that plows through anything. It takes literally less than a minute per arch. If it were me, I would stack them up 3 or 4 high and make multiple circles at one time.

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[Byron Lu]

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.

[Kevin Jenness]

A reasonably rugged cnc router with a vacuum table will give excellent results far faster than your laser. Cabinet manufacturers commonly cut 3/4" material in one pass- even my unit with a PC 7518 router will do 1/2" material in two passes with a 1/4" compression bit with clean surfaces both sides. Load the sheet, cut eight circles, repeat. Look for a cnc equipped shop in your area to sub the task, it will be far more profitable than cutting blanks and spinning them on a bandsaw you don't have.

[Jerome Stanek]

the cnc would be the best way if you need no holes in the center or prefect circles every one would be the same. and If no it would be just as fast if not faster throw a 4x58 sheet on hit go 5 minutes later you have 6 perfect circles with a slower cnc. I could cut that down with a bigger bit but I was using a 1/4 inch cutter

[David Buchhauser]

WOW thanks so much for the replies. It seems the consensus is to use a bandsaw to cut 3-4 pieces each time. Sounds like the most efficient way. CNC routers will be quite bit slower as I understand.

Other parameters: I need the edge to be clean and smooth. A tiny hole on the back of the circle will be okay but not on the face side. Would be nice if no hole at all.

I can usually cut a 4x8 into 8 pieces of 24" rounds (well 23.5" each instead). The laser edges are very smooth but with the brown burning edges. Can a band saw cut it with a smooth edge?

I can only use a single phase bandsaw if this is the direction to go as it will stay in my garage. Any recommendations on what type/brand/config of the bandsaw suitable for my purpose?

Again thanks so much for your help!

Byron,
Could you cut them slightly larger in diameter, then sand off the burned edge. Perhaps you could post a photo of one of your finished parts so we can see the actual extend of the "burned edge".
David

[Mel Fulks]

A router with a SINGLE FLUTE bit would cut fast and real accurate. Band saw is good too ,but a little less accurate.

[Matt Day]

I’d make a jig to cut on the bandsaw, then a jig at a sander to clean the edges. Both using a 1/4 deep peg in the center. Might be able to freehand the sanding at a disc or edge sander.

[Lee Schierer]

I’d make a jig to cut on the bandsaw, then a jig at a sander to clean the edges. Both using a 1/4 deep peg in the center. Might be able to freehand the sanding at a disc or edge sander.

A jig on a router table would give you faster clean up.

[lowell holmes]

I would cut the wood into squares and then cut the circles from the squares.

[Byron Lu]

A router with a SINGLE FLUTE bit would cut fast and real accurate. Band saw is good too ,but a little less accurate.

Are you talking about a CNC router? So to cut through a 1/2" thick plywood, how many passes do I need for a router with a single flute bit with good speed? Thx

[Byron Lu]

I would cut the wood into squares and then cut the circles from the squares.

Which method is fastest to cut from squares to circles? bandsaw?

[Art Mann]

I own a cnc router and I cut 1/2 inch plywood with it fairly often. First of all, I don't know why one would want to use a single flute bit. A quarter inch 2 flute compression bit like someone else already mentioned would cut faster and produce dramatically better cut quality. I don't have a very powerful spindle but I would cut at 150 inches per minute and I would cut it in 2 passes. A 24 inch circle would take about 20 seconds if my calculations are correct. A fast machine could cut it in a single pass at 300-400 inches per minute. How much do you want to spend on a machine?


Are you talking about a CNC router? So to cut through a 1/2" thick plywood, how many passes do I need for a router with a single flute bit with good speed? Thx

[Mel Fulks]

Are you talking about a CNC router? So to cut through a 1/2" thick plywood, how many passes do I need for a router with a single flute bit with good speed? Thx

Not CNC ,just ordinary router. One pass with single flute router bit, drill one hole thru which bit is dropped

[Darcy Warner]

BS, then pin router. Fast and perfect.

[Mel Fulks]

A single flute bit cuts faster for the same reason a 5 point hand saw cuts faster than a 10 point. OP doesn't have a CNC

[johnny means]

I had to cut circles from .75" PVC a couple of days ago. I cut square blanks, marked drilled center holes, then routed with router that I keep mounted to a circle jig base. Took me a grand total of about 20 minutes to make four of them. IME, a human with a good setup cuts circles faster than a CNC, but setting up the several tasks necessary eats up any time saved.

[Marc Jeske]

It seems the main, or only complaint OP has is "sanding the brown edges" from the laser, and does not want pin hole in center.

Any bandsaw stacked blanks, or router cut will need even more sanding. so no benefit there.

Dedicated router table would be great for cleanup, but probably not overall better than current sanding.

So, there seems to be no improvement in process here yet.

OP did not say how well the "brown sanding" is going.

Maybe the answer is to continue w the laser cutting, but develop a more specific dedicated edge sander....
Attachment table to a oscil edge sander for example.


Marc

[Byron Lu]

Thanks for your info on a cnc router. I just did some research and axiom ar8 pro/elite vs camaster stinger II seem to be good choices here. I am okay spending 6k to 12k if I have to. If a much cheaper bandsaw solution serves the same purpose, I will go that route.

I just want a FAST solutions - right now my need is about 150 rounds (24" or 18") per month.

[Byron Lu]

So I still need sanding the edges of the circles cut via a cnc router or a bandsaw?
Right now the circles I laser cut has very smooth but brown edge. I am using a belt sander by holding the circle vertically and rotate as I sand. Since all the circles are stained afterward, some stains (lighter stains such as antique white) require cleaner sanding.

My current complaints about laser cut circles: 1. slow speed, at about 30 inches per minute, so each circle takes almost 3 mins to cut; 2. brown edges requires sanding.

So if other methods also require sanding, then I could still benefits from having a higher productivity with shorter time spent on cutting all the circles?


It seems the main, or only complaint OP has is "sanding the brown edges" from the laser, and does not want pin hole in center.

Any bandsaw stacked blanks, or router cut will need even more sanding. so no benefit there.

Dedicated router table would be great for cleanup, but probably not overall better than current sanding.

So, there seems to be no improvement in process here yet.

OP did not say how well the "brown sanding" is going.

Maybe the answer is to continue w the laser cutting, but develop a more specific dedicated edge sander....
Attachment table to a oscil edge sander for example.


Marc

[David Buchhauser]

Hi Byron,
I think that the beauty of using a cnc router like the ones you have mentioned is that your process will be faster and less labor intensive than some of the other band saw suggestions. This could possibly free you up to work on another job while the cnc is running the circles, and I would think that there would be very minimal cleanup and/or sanding of the edges. In my business (metal machining) I often have one or two of the cnc machines running parts while I am working on other parts on the conventional mill or lathe.
David

[Byron Lu]

Yes, I can see your point here. My goal is to reduce the total time/effort to cut circles in bulk. The bandsaw method and manual router method all require pre-cut into smaller squares vs a CNC table (say 4x4') I can just send a half sheet in and come out with four circles). I guess my ultimate question is: which way will save me time when I cut them in bulk.


I had to cut circles from .75" PVC a couple of days ago. I cut square blanks, marked drilled center holes, then routed with router that I keep mounted to a circle jig base. Took me a grand total of about 20 minutes to make four of them. IME, a human with a good setup cuts circles faster than a CNC, but setting up the several tasks necessary eats up any time saved.

[Byron Lu]

I agree with you on this. Since I never run a cnc router, I wonder how much prep/setup I need in order to cut, say, 30 half sheets (4 x 4') of 1/2" maple plywood? Clamping down/ deassembling takes much time?


Hi Byron,
I think that the beauty of using a cnc router like the ones you have mentioned is that your process will be faster and less labor intensive than some of the other band saw suggestions. This could possibly free you up to work on another job while the cnc is running the circles, and I would think that there would be very minimal cleanup and/or sanding of the edges. In my business (metal machining) I often have one or two of the cnc machines running parts while I am working on other parts on the conventional mill or lathe.
David

[David Buchhauser]

https://www.youtube.com/watch?v=OgYCGaPPaeI (https://www.youtube.com/watch?v=OgYCGaPPaeI)
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[David Buchhauser]

Hi Byron,
Notice that the parts being cut in the video have small tabs to hold the parts in place after the final pass with the router bit. He breaks the parts out with a chisel and probably does some sanding to smooth them out. If he had a vacuum table to hold the plywood down, then these tabs would not be necessary.

So I suppose that it depends on how much more a vacuum system adds to the cost of a cnc router like the ones you have mentioned (or the one shown in the video). If you really want to know what the edge finish will be like, you might consider paying a visit to one of your local production cabinet shops who have a large cnc and pay them to run a few sample parts for you (circles) with your material. You will find out what bit they use, cutting speed, number of passes, edge finish, etc. to see if the results and time savings are worth the investment cost for a new cnc router.
David

[Byron Lu]

I just looked at the Axiom Pro+ series, and it has the following speed specs:


Spindle Configuration
ER20


Included Collets
1/4" & 1/2"


Electro Spindle
2.2KW


Spindle speed
0~24000 RPM


Rapid feed rate
200 IPM (5 MPM)




Do you think that machine still needs two passes to cut 1/2" plywood? How about their next up machine Elite series with a rapid feed rate of 320ipm?


I own a cnc router and I cut 1/2 inch plywood with it fairly often. First of all, I don't know why one would want to use a single flute bit. A quarter inch 2 flute compression bit like someone else already mentioned would cut faster and produce dramatically better cut quality. I don't have a very powerful spindle but I would cut at 150 inches per minute and I would cut it in 2 passes. A 24 inch circle would take about 20 seconds if my calculations are correct. A fast machine could cut it in a single pass at 300-400 inches per minute. How much do you want to spend on a machine?

[Marc Jeske]

Seems to me ANY other cutting tool will have more tearout of face grain than the existing laser that will be more labor to sand out than the existing laser produced "brown"

Seriously - Spend the $$$ on a computer xy machine to JUST CUT CIRCLES ??

AND, you will STILL, depending, probably want... have to sand edges anyway even w no face grain tearout.

Slow down, think this through, and Keep that $$$ in your pocket.


Solution - Cut as you have been cutting... but setup a faster sanding system... 1.001 ways to DIY do that economically and simply.

If nothing else mount a belt sander 90 degree to a 2x2' dedicated flat workbench... or make fancier.

Even though a center hole would make for more possible methods, even without that a simple fence could be made to speed and accurize the sanding and eliminate any hand pressure/ motion error.

Step by step quasi osscilate w 1/2" ply sub 24" round rotating sled elevator.

If funds available, buy a osci edge snder and mount a 2x2 table against it... and again, somekinda limiting fence.

How bout a center SMALL like 1/16 - 1/8" pinhole that is patched at end of fabbing ?


Marc

[Marc Jeske]

OP said - "I am using a belt sander by holding the circle vertically and rotate as I sand."

If nothing else... Like I said above - Strap that sander down horizontally, secure a 2x2 table against it to make the most basic edge sander.

Stop vertically holding and balancing your workpiece... VERY inaccurate in ALL directions, let alone mentally and physically tiring compared to just doing above.

Marc

[Art Mann]

I would like to know where you got that information. I don't mean to be impolite but I have a lot of experience to the contrary. A bit moving through a piece of plywood has no knowledge of whether the motive force is human or electrical. As you can read above, the OP is interested in new equipment, including a CNC router, if it fits his requirements. That is why I brought it up. He was under the false impression that a laser cutter will cut as fast as a CNC router, which is not correct.


A single flute bit cuts faster for the same reason a 5 point hand saw cuts faster than a 10 point. OP doesn't have a CNC

[Rob Luter]

I could be wrong, but my gut is telling me a 4x8 sheet should be good for six pieces 24” in diameter.

Only if the router bit is 0.0" in diameter.

[Kevin Jenness]

The o.p. said "I can usually cut a 4x8 into 8 pieces of 24" rounds (well 23.5" each instead)."

Any cutting method is going to require some sanding depending on the finish requirements. If the circles are cut with a compression bit in a cnc router at a reasonable speed the cleanup will be faster than sanding out burn marks from a laser or the corrugations from a bandsaw, and the faces will be free of tearout due to the bit design. A circle jig on an oscillating edge sander would probably be the way to go for quantity production.

I expect the Axiom router mentioned with a 2.2 kw spindle will cut 1/2" ply with a 3/8" bit in one pass but overall machine rigidity and the hold-down method have to be stout enough to counter the cutting forces to get a good result. A vacuum table is the best option for this sort of work. There are a lot of options out there so do your research and try to "buy the cnc you need the first time".

As suggested previously, it would pay to sub out a batch to a cnc shop to see the process and assess whether a router would be a good investment- it definitely can add a great deal of capability to a small shop.

[Brian W Evans]

We don't know what you're making, or what else you make, so it's hard to tell if a CNC would be the right choice for you financially. It does seem like it has the potential to speed things up quite a bit, but if you've got nothing else to do while it's working or if your profit margins are thin, it might not make sense.

IMO, the next best option is to improve the sanding process. Definitely don't do it vertically - get some kind of oscillating belt sander and make a table, as others have suggested. The easiest way is with a hole in the center of the circle and a pin to index off of. If you don't want the hole, here's a possibility:

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Cut out a very slightly bigger circle from a sheet of ply and mount it on top of a solid sheet. Sand or cut the jig along the top until it just kisses the top of the circle, leaving a small opening. Mount the jig to your sander. To sand, drop your rough/brown circles into the hole and rotate by hand.

Frankly, circles will always be easier with a hole in the center. Can you use a dowel or some putty to fill the hole?



Edit: Sorry, decided to edit my diagram after posting, but couldn't figure out how to delete the previous versions.

[Gregory King]

Not sure if it was mentioned, but sanding the edges could be done using a pivot point on a sturdy disc/ belt sander setup. Such as the cutting setup on the bandsaw. Mount the pivot point so that it slides to the desired point of contact complete with a stop. Dare say you can sand very quickly with a 120 grit disc.

[Bill Space]

Only if the router bit is 0.0" in diameter.

Since the OP really only needs 23.5” the point is moot, as he likely can get 8 pieces from a 4x8 sheet.

But it if he really needed 24” or slightly larger circles, couldn’t he get six of them out of a 4x8 sheet by offsetting the center points of the circles somewhat? Wouldn’t work for rectangles or squares, but with circles it would probably even be possible to get six circles larger than 24” diameter. This is what my minds eye was telling me...

Apologies to the OP as this really is a tangent to his question.

[Brian Holcombe]

Seems like the perfect job for an Aigner Cirquick mounted to a shaper after the part is cut oversized via laser.

[Jerome Stanek]

So I still need sanding the edges of the circles cut via a cnc router or a bandsaw?
Right now the circles I laser cut has very smooth but brown edge. I am using a belt sander by holding the circle vertically and rotate as I sand. Since all the circles are stained afterward, some stains (lighter stains such as antique white) require cleaner sanding.

My current complaints about laser cut circles: 1. slow speed, at about 30 inches per minute, so each circle takes almost 3 mins to cut; 2. brown edges requires sanding.

So if other methods also require sanding, then I could still benefits from having a higher productivity with shorter time spent on cutting all the circles?

If you use the correct bit there is no sanding and speed is more then doubled what you are cutting now. Big advantage is less likely to catch fire.

[Keith Outten]

A CNC Router with a 1/4" bit and two passes less than 40 seconds for each disk.
If you use tabs instead of a vac hold down system that is pretty expensive you cut the tabs with a multi tool, 20 bucks at Harbor Freight and it takes less than 5 seconds to cut each tab. A couple hold down screws into the spoil board and your total time per disk is easily under 90 seconds each.

[Malcolm Schweizer]

I don’t know how else to post it, but it is simply a piece of plywood with a plane ol’ Screw at the pivot point. One issue is it won’t be perfectly smooth, so you would need to sand it. A CNC would cut a smooth edge, but if you don’t have a CNC, then that’s a huge cost, and big floor space. The slower you go, and the sharper your bandsaw blade, the smoother the cut will be with a bandsaw. Use double stick tape to keep the stacked pieces together. It shouldn’t take much force with a decent bandsaw, so the tape doesn’t have to be much- just enough to prevent the pieces from slipping.

Another option is to cut slightly larger and then use a straight cut router bit to trim to a smooth edge with a circle template or a circle jig on a router table- basically the same jig as on the bandsaw.

[Brad Shipton]

All CNC's are not created equally. Hire someone with an industrial machine if that is the route you want. A real machine will cut in a single pass if they have enough vacuum, which a pro should have. If hold down is a problem, they will use an onion skin pass (final pass 0.03" or so). The key to this will be finding 49" wide sheets in the species you want or using BB. At this scale you will find industrial guys are interested. They could crank out a couple of months of pieces in short order and you stack on a rack. A pro machine should result in zero clean-up, but smaller machines like the one you posted could suffer from chatter that will lead to 5 - 10min per piece sanding.

Here is a video of high speed production if you have a spare $200-300k+ to spend. https://www.youtube.com/watch?v=uffr3lLlRV4

Key thing to look at in original post: 50 - 100 pieces per month.

[Byron Lu]

Thanks for the link. That is very fascinating to watch. I do not have that kind of cash or plan though.

My monthly rounds for exact now are 100 pcs of 23.5" rounds and 70 pcs of 17.7" out of 4x8' 1/2" maple plywood sheets.


All CNC's are not created equally. Hire someone with an industrial machine if that is the route you want. A real machine will cut in a single pass if they have enough vacuum, which a pro should have. If hold down is a problem, they will use an onion skin pass (final pass 0.03" or so). The key to this will be finding 49" wide sheets in the species you want or using BB. At this scale you will find industrial guys are interested. They could crank out a couple of months of pieces in short order and you stack on a rack. A pro machine should result in zero clean-up, but smaller machines like the one you posted could suffer from chatter that will lead to 5 - 10min per piece sanding.

Here is a video of high speed production if you have a spare $200-300k+ to spend. https://www.youtube.com/watch?v=uffr3lLlRV4

Key thing to look at in original post: 50 - 100 pieces per month.

[Byron Lu]

You are correct: nominal 24" circle, actually 23.5". So yes 8 circles per sheet currently.



Since the OP really only needs 23.5” the point is moot, as he likely can get 8 pieces from a 4x8 sheet.

But it if he really needed 24” or slightly larger circles, couldn’t he get six of them out of a 4x8 sheet by offsetting the center points of the circles somewhat? Wouldn’t work for rectangles or squares, but with circles it would probably even be possible to get six circles larger than 24” diameter. This is what my minds eye was telling me...

Apologies to the OP as this really is a tangent to his question.

[Byron Lu]

Thank you so your excellent suggestion about the edge sander setup. I know I have a very primitive approach to the sanding part and it IS tiring mentally and physically!
Your point of not spending top dollars to just cut circles is well taken!
I will contact a few cabinet shops tomorrow to see how much it cost to sub it out.


OP said - "I am using a belt sander by holding the circle vertically and rotate as I sand."

If nothing else... Like I said above - Strap that sander down horizontally, secure a 2x2 table against it to make the most basic edge sander.

Stop vertically holding and balancing your workpiece... VERY inaccurate in ALL directions, let alone mentally and physically tiring compared to just doing above.

Marc

[Rob Luter]

You are correct: nominal 24" circle, actually 23.5". So yes 8 circles per sheet currently.

Missed that. I had 24” on the brain. :o

[Jim Morgan]

Byron, if you want to see the pictures others have posted, toss in $6 to become a SMC contributor.

[Jerome Stanek]

You could also get by with a 24x24 cnc and just cut your blanks as you would for the laser. Once setup and a small vacuum pump with a dedicated fixture you would be able to knock them out in no time. Something like this would get you going pretty quick. As Keith said you could use tabs But I would get an Amama 3/16 flush cut and a small trim router to remove the tabs I do this sometimes and the 3/16 bit fits in the 1/4 slot

https://www.automationtechnologiesinc.com/products-page/industrial-level-machine-cnc-router/kl-6590-36%e2%80%b3-x-25-6-mach3-usb-connection-spindle-relay-control/

[Roger Feeley]

I could be wrong, but my gut is telling me a 4x8 sheet should be good for six pieces 24” in diameter.
bill, You have to allow for the kerf. The operative question is whether the circles must be a FULL 24”. If so, any kerf at all pushes them over and the yield is 3/sheet.

correction. I see where you were going. I stand corrected and concur on 6/sheet.

[David Buchhauser]

Actually 8 per sheet for 4 x 8 sheet for the 23.5" size specified with 1/4" bit.

[Byron Lu]

Byron, if you want to see the pictures others have posted, toss in $6 to become a SMC contributor.

Thank you. I did not know this trick.

[David Buchhauser]

Hi Byron,
What other kinds of parts do you make from wood, and would any of your other parts lend themselves to manufacture on a cnc router? It would be nice to get a new cnc machine to start paying for itself as soon as possible. With your experience running your cnc laser cutter, it would not be too much of a learning curve to start running the cnc router.
David

[Pete Staehling]

I’d make a jig to cut on the bandsaw, then a jig at a sander to clean the edges. Both using a 1/4 deep peg in the center. Might be able to freehand the sanding at a disc or edge sander.
That would be my choice as well, if you even need the jig at the sander. If you get a clean enough cut at the band saw running a ROS quickly over the edge may be enough and if the sanding is light enough freehand may be fine. The sanding might be done on a stack of disks at once.

[David Buchhauser]

Pete,
It's very hard to get the accurate cut that may be needed for this with a band saw. It can be very hard to follow a line, even with a circle attachment. Depending on the tolerance of the part, for repeatable results the cnc is the way to go. Either cnc laser or cnc router.
David

[Carl Beckett]

If you end up sanding the edges, I would look at an oscillating edge sander. Laying the pieces flat on a table against an oscillating belt would be night and day improvement over your current sanding method.

[Jon Endres]

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.

[Jay Kepley]

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-299-111-00-Table-Balance-Sanding/dp/B000P4O7DW?source=ps-sl-shoppingads-lpcontext&psc=1

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

[Timothy Orr]

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 isn’t 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.

[Alex Zeller]

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.

[Davis Young]

Six would be correct.

[Mike King]

Bandsaw using a circle jig. Pattern rout to finish.

Mike

[Thomas C Barron]

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

It’s a 2’ 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.

[Thomas C Barron]

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 shouldn’t require any edge sanding.

[lowell holmes]

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

[lowell holmes]

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.

[Wayne Cannon]

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.

[Biff Phillips]

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.