Best way to cleanly cut a 36" diameter circle from 3/4" Birch plywood???

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Forum topic by barringerfurniture posted 03-06-2015 08:10 PM 3068 views 0 times favorited 15 replies Add to Favorites Watch
View barringerfurniture's profile


224 posts in 1916 days

03-06-2015 08:10 PM

Topic tags/keywords: question milling router bandsaw plywood

Has anybody done this with clean results (edges square to face, consistent circle, no tear-out, etc.)?

Don’t want to use a jigsaw because of how the blade flares out when going around curves. My experience with a router and plywood in the past resulted in tear-out issues (though that was when cutting a rabbet). Band saw seems awkward and difficult because of the size of these table tops – 36” diameter.

I know to tape it to prevent tear-out. Any other suggestions?

Thanks folks.

-- Scott Barringer, Sacramento, CA

15 replies so far

View SirIrb's profile


1239 posts in 1434 days

#1 posted 03-06-2015 08:14 PM

Router. I believe that will give you the best cut. Trace the circle with a razor knife first to avoid tear out.

-- Don't blame me, I voted for no one.

View waho6o9's profile


8525 posts in 2781 days

#2 posted 03-06-2015 08:17 PM

There are compression bits to help reduce tear out and I have a couple on the way
but haven’t used them yet. One’s with the bearings and the other is w/out bearings.

View OnhillWW's profile


144 posts in 1436 days

#3 posted 03-06-2015 08:26 PM

I assume you are talking about tear out along the edge and not splintering at the faces? For face splintering I would use a router w/ a quality solid carbide down spiral bit and make the first two passes shallow and slow with the rest slow enough to not create pull out. Admittedly your success will vary with the quality of the plywood. If the issue is edge pullout cut the circle slightly oversize using any method you like; make a jig (a pin located 18” from the sanding surface)which will allow you to run the top against a stationary disk or belt sander loaded with good 80 grit paper and sand to the line, slow enough so that you avoid burning, dress the abrasive often with a crepe rubber cleaner stick. That’s all I got…

-- Cheap is expensive! - my Dad

View Yonak's profile


986 posts in 1725 days

#4 posted 03-06-2015 09:51 PM

If you can have a hole in the center of the disk, my favorite way is to rough cut it with a sabre saw and then sand the edges smooth on the disk sander. You have to devise a jig that’s got a pin firmly fixed 18” from the sanding disk.

View firefighterontheside's profile


19454 posts in 2060 days

#5 posted 03-06-2015 09:56 PM

Could do it with a bamd saw. Need some sort of support that is bigger than the band saw table. You’ll need a small nail in the center for the piece to pivot on. Start with a square piece 36×36 put the flat side against the blade and start turning.

-- Bill M. "People change, walnut doesn't" by Gene.

View pintodeluxe's profile


5798 posts in 3017 days

#6 posted 03-06-2015 09:58 PM

I made a circle cutting jig for my router. The holes are placed very closely together, so I can rout out the shape first. Then I decrease the cutting diameter slightly by moving the jig to the next hole. This final trimming pass with a 1/4” spiral bit yields a very clean cut. Since you will be cutting it upside down, technically you would want an up-spiral bit. The bits are inexpensive compared to larger diameter or specialty spiral cutters shown above.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View InstantSiv's profile


262 posts in 1799 days

#7 posted 03-06-2015 10:10 PM

If you don’t want tear out rough cut the ply and flush trim with a 36” template.

View TheWoodenOyster's profile


1317 posts in 2139 days

#8 posted 03-06-2015 11:40 PM

Router and a compass jig. That’s how I have done it. Whiteside router bits will help minimize the tearout, though in plywood it is tough to do away with it altogether.

-- The Wood Is Your Oyster

View English's profile


660 posts in 1681 days

#9 posted 03-06-2015 11:57 PM

In the picture below I cut a 36” half circle, I was making a table top that was to have two leafs. Complete circle would be just as easy. My jig clamps to the band saw and I use a wood dowel for the center pivot. I have made 6’ circles down to 12” with this jig.

-- John, Suffolk Virgina

View MT_Stringer's profile


3183 posts in 3435 days

#10 posted 03-07-2015 12:01 AM

OOPS! Guess I am a slow typer today. :-(

It seems to me you could turn the table over onto the topside and use a router jig that would pivot around a point in the middle. Rough cut close first with a jig saw, then run the router around it.

-- Handcrafted by Mike Henderson - Channelview, Texas

View Ghidrah's profile


667 posts in 1426 days

#11 posted 03-07-2015 01:10 AM

Get a template guide and match the OD with a forstner bit. Bore the hole in a piece of 1/2” ply 24” long and at least as wide as the router base. Snap a line through the template hole to the end of the ply. You’ll probably need to modify the hgt of the template guide so as not to protrude through the bottom on the ply. Circle or disc? Circ hook on bit meas to 18” along snapped line mark at 18”. Disc, butt tape to bit meas 18” on ply along the snapped line to 18”. As previously mentioned 1/8” down or up spiral bit works well, make shallow cuts and take your time to avoid ragged edges.

-- I meant to do that!

View barringerfurniture's profile


224 posts in 1916 days

#12 posted 03-07-2015 01:36 AM

Thanks for all the help everyone. I think I’ll try a router attached to radius jig somehow (like a compass), pinned to the center and a down spiral bit. We’ll see how it goes. I have to make seven of them. If it doesn’t work well with the first, I’ll clean it up and try something else the second time.

How bad could it be?

Thanks again.

-- Scott Barringer, Sacramento, CA

View rick1955's profile


264 posts in 1635 days

#13 posted 03-07-2015 04:46 AM

Another technique is the table saw using a pivot point or a pattern fence. Rough saw the circle with a jig saw or bandsaw first.

-- Working smarter with less tools is a true crafts person...

View barringerfurniture's profile


224 posts in 1916 days

#14 posted 03-11-2015 01:52 AM

Thanks for all the tips guys. Ended up getting a 1/4” up-spiral bit from Whiteside. Worked great with a hand-held router and a quick, shop made compass jig. No tear-out even on the up side, nice, square edges, etc.

Thanks again.

-- Scott Barringer, Sacramento, CA

View BacktotheWood's profile


125 posts in 3225 days

#15 posted 03-12-2015 12:30 PM

Way to go Scott. This forum is awesome for getting help. English’s method using a bandsaw works well too. It’s not as awkward as it may seem but it does need a large table or extension on the bandsaw.

Keep making sawdust,

-- Bob, --Silence & smile are two powerful tools. Smile is the way to solve many problems & Silence is the way to avoid many problems.

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