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.
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.
A hexagon is 360 degrees divided by 6 sides = 60 divided by 2 = 30 degree
I'd use the very high grade plywood I could buy (has better interior
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
Actually when I googled, I saw only 4 sided boxes plus a top and bottom.
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.
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.
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:
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.
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
Good Luck with your drums.
"If thy neighbor offend thee, buy each of his children a drum." -
Ancient Chinese Proverb
Would this be an example of what you are talking about?
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...
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
When starting at a corner, include a sacrifical piece to avoid tear out.
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.
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