How to get nice corners on a plywood box.

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I am going to build a couple of cajon's for my sons for Christmas. These are basically a plywood box with 6 sides with a hole for sound that is used as a drum. If one does a google image search for "cajon drum" you will see many fine examples. But they all appear to have nice sort of rounded corners and edges. They are made in some variation of plywood generally 1/2 and 1/4 inch. Does anybody have some good tips on how best to get this look when joining plywood? I will be using Birch, probably 1/2 in for the sides, top and bottom, 1/4 inch for the front and back.
Thanks, Jim
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Jim, I assume you're trying to avoid tearout. I use two methods. The best is to use a piece of sacrificial wood and cut both pieces at the same time.the tearout occurs where the blade exits the wood on the cut. A little experimentation will show you what to do. The second method is to use duct tape over the cut (prior to the cut), which is removed after the cut.
Also, make sure you use a good blade that is sharp.
jtpr wrote:

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Looks like I misunderstood the question.....Sorry.
Never Enough Money wrote:

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Jim, I'd use a 1/4" round over bit in a router to ease the edges and corners.
DonkeyHody
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My Suggestion: A hexagon is 360 degrees divided by 6 sides = 60 divided by 2 = 30 degree cuts. I'd use the very high grade plywood I could buy (has better interior layers). Cut very clean angles using a good blade at 30 degrees. You will need a spline in each joint or it will not have very much strength (1/2" ply doesn't have much glue area at the joints). This will require a jig to run each side through the table saw to cut a dado at 90 degrees. Glue up and lightly sand corners being careful not to sand through the top layer.

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jtpr wrote:

I would use a solid corner with rabbeted sides so the plywood would fit flush. The exposed corner of the wood could be rounded much cleaner than trying to round off a piece of plywood. I made a chest this way and it turned out nicely.
--
Gerald Ross
Cochran, GA
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I will post a drawing on Alt.binaries.pictures.woodworking showing what I was talking about. The rabbits can be done with a jointer, router or even with a table saw. After sanding level I then round over the corner. Good luck, however you do it.

--
Gerald Ross
Cochran, GA
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Gerald,
Thank you so much for taking the time to post the drawings. I believe I will go that route. I think a contrasting trim might look nice, maybe a lacewood or cocobola.
-Jim
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You can build them? I thought boys were born with them, no?
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I like TomH's idea best so far.
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"jtpr" wrote:

Box joints, rounded over after assembly, are tough to beat IMHO.
Lew
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You're right..and they're quick too...and easy to assemble.
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Wow, thanks for all the ideas. I guess it is a four sided box with a top and bottom. That's kind of what I meant by six sides. Anyway, this is a picture of what I would like to end up with:
http://www.esflamenco.com/img/imagenesgrandes/25712723-147.jpg
Looking at the edges on this it appears that DonkeyHody's suggestion would come the closest to the edges in the picture. Do I assemble and glue up then run the router over the edges? Any technique here to avoid tearing? I'm gonna use A4 Birch, seems to be the best I can find in my area.
-Jim
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jtpr wrote:

Thanks, Jim, but actually I like Gerald's idea better. If you have the tools and skill for it, glue a 1/2+ X 1/2+ strip of some contrasting wood to the edges of half your pieces. Let it stand a little proud on the surface that will show. Then glue your box together so you have these contrasting solid wood strips at each edge. Use a top bearing flush cut router bit to trim the edges flush with the plywood, THEN use a 1/4 round-over bit to soften the edge. It will look much better than the rounded-over plywood.
But if you choose to just round the edges of the plywood like I originally suggested, the only tearout problem you will have is at the corner where you begin to go across the grain of the surface ply. Do the edges that go with the grain first. Then, on the cross-grain part, start your cut about an inch away from the corner and go backwards (climb cut) that inch back to the corner. The 1/4 bit won't grab enough to take the router away from you like a more aggressive bit might.
Good Luck with your drums.
DonkeyHody "If thy neighbor offend thee, buy each of his children a drum." - Ancient Chinese Proverb
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Would this be an example of what you are talking about?
http://www.taunton.com/finewoodworking/pages/w00119.asp
If it is, I like it. But if I'm using 1/2" ply on the top, bottom, and 2 sides and 1/4" on the front and back faces, as advised by drum builders, wouldn't this be tough to accomplish?
Actually, now that I think about it, I would only have to do this on the 2 sides and the top...
-Jim
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jtpr wrote:

Jim, I was thinking the whole box would be 1/2" ply. If two sides are 1/4", you have to get more creative. I don't have a ready idea for that. Let it ferment a while.
DonkeyHody
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jtpr wrote:

Yes
Mount router in table and use fence with rounding over bit to insure that your piece is following a straight reference (fence) rather than use a bit with a pilot bearing and allowing the bit to follow the assembled edge.
When starting at a corner, include a sacrifical piece to avoid tear out.
Have fun.
Lew
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I climb cut about an inch on end grain roundovers to avoid tear out as it seems easier than the sacrificial piece.
On Tue, 29 Nov 2005 22:35:46 GMT, Lew Hodgett

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jtpr wrote:

Baltic birch may be the better choice, it is birch all the way through, most cabinet plywoods have poplar interior veneers. Luthiers use plywood that is all hard maple, there is a luthier newsgroup under the rec.crafts hierarchy.
--

FF


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I used this bit on 1/2' plywood to makd a open top roll around toy box for my grandson. Strong and looked great. http://www.infinitytools.com/products.asp?dept 62 . .

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