Built Your Own Cajon (a Drum) for Less Than 25.- Euro

A Cajon is a south american drum made completely out of wood. It is played by slapping the front face with your hand and it's perfect for unplugged sessions because it could substitute a whole drumset. 
This instructable shows you how to build a perfect Cajon for about 25.- Euros and only a few hours of work.
It is perfect for schools as the steps themself are short. They only take 30-60min. each but you have to wait each time for a day to let the glue dry.
And you don't need many tools, an electrical drill is essential, all other steps might also be done with manual tools (jigsaw, screwing...)

The result is an individual Cajon that meets even high standards. I chose the size so that it will also fit in any commercial bag, which you might want to buy.

Step 1: You Need

Tools:

an electric drill with 2mm drill bit, can also use a cordless screwdriver for this job
a jigsaw (electric or manually operated)
a screwdriver (electric or manually operated)
some wood glue
a tape measure or ruler (30cm is enough)
4 clamps or something heavy like a set of filled water bottles

Materials:

You need six pieces of wood to built the box. The best and most common wood that you can take for this job is birch multiplex. Every hardware store should have this and they could also cut it for you to the right size.

For one Cajon we need:
2 pieces of 300 x 300 x 12 mm (bottom and top)
2 pieces of 300 x 476 x 12 mm (side parts)
2 pieces of 300 x 500 x 4 mm (front and back)
 4 pieces of 290 x 12 x 12 (not multiplex, I used pine, because it is rather cheap, this can be made from a rectangular block of wood, doesn't have to be birch, also the size doesn't have to be exact 12, can also be 10 or 14)
some screws of 2.5 x 16mm and 2.5 x 20mm
some knobs for the foot.
and optionally: a set of snare wires, the longer the better, 35cm or 14" is ok.

Cost:
wood: < 20.- ( I got mine for 16.-)
snare wires: ~ 5.- (I paid 7.- (optionally)
screws and glue: 2.- (had it at home already)
knobs: 4pieces 1.- (also had it at home)

Total: 23.- to 30.- Euros

Step 2: The Size of the Wood Pieces

The length of the side parts is the 500mm minus twice the thickness of the birch multiplex. So if you only get Multiplex with a thickness of 14, adjust the length of the side parts to 472mm (500mm - (2*14mm) = 472 mm)
The size of the 4 stabilizing sticks is not so critical, they can also be 280mm long and 10mm or 14mm thick, you'll see later why. Buy a cheap rectangular block of wood and cut the pieces by yourself, thats quite easy. Multiplex is very stable in large pieces, but if you cut it in small pieces, the layers might disintegrate!

That's all, let's start!

Step 3: Cut the Long Rectangular Block of Wood

First of all cut the long rectangular block of wood to the desired pieces of 290mm. File down the edges if there are any splinters left from the sawing.

Now look at the two thin wood pieces and choose which of them should be the front and which the back. Once you decided this, you should take care not to damage or to soil the outer surface.

Step 4: Cut the Sound Hole

Now take the back one and mark the circle for the sound hole. I chose to position it at 2/3 of the height. The exact size and position doesn't matter too much. Just try to get a harmonically look. For me the center of the hole was 15cm from each side and 17cm from the top. Then I used and old CD to draw a perfect circle prior to cutting it out with the jigsaw.

After that I thought I would have rather made a flower than a perfect circle, but ah, may be the next time.

After finishing the sawing use a file to eliminate still existing corners and finally break the rim with sandpaper to get a smooth surface.

Step 5: Drill the Holes

Now it is time to drill the front and backside. The lower front side is glued to the frame, so you don't need any holes here. The backside is completely screwed. This way you can open it for service. ;-)
Get the holes at a distance from the rim of half the thickness of the side parts. If they are 12mm thick, drill the center at 6mm from the rim. Either measure it, or draw the thickness of the side parts to the rim of the backside.
Think about the distances by yourself or just use the ones that I propose.
For the long side use 4cm from each end and 6cm from screw to screw. (8x)
For the short side use 3cm from each end and also 6cm from screw to screw. (5x)

Mark the center of the hole and drill with a 2mm drill bit. And use some old scrap wood when drilling to avoid the lower side to break out.

Step 6: Make Countersinks

Now take another piece of sand paper and sand down the edges of the holes. Then take a countersink cutter and make the holes wider for the head of the screws. If you don't do this, either the screw will not sink completely into the surface or the wood could crack.
Sand down the edges another time after that.

Now take the front part and mark the holes for the screws. I suggest to use fewer screws than on the back side. The top half of the front must be loose to be able to swing and produce a good sound. I suggest to use 2 screws on the long side, the first 6cm from the edge and the second 8cm from the first. And 4 screws on the short side, 3cm from the edge and 8cm from each other. That looks good.

Step 7: Glue Rectangular Block of Wood to the Side Parts

Now that everything is prepared, take the rectangular blocks of wood and glue one of them to each end of the long side parts. It is very important to get the two edges real smooth, as there will be the bottom and top side glued to the sides. So first add some wood glue and let it dry for a few minutes. Don't use too much glue, as this will cause the two parts to swim on each other, making it difficult to adjust them. Then get them together and adjust the edge. If everything is o.k. carefully close the clamps and press the two parts together. The wood glue needs a few hours to dry down and while this time don't touch it.

After the glue is dried you can drill 3 holes into the rectangular block of wood and screw some of the long screws (2.5x20) inside. If you get only 10mm multiplex and 10mm blocks, you should take only 16mm screws! Also be careful not to drill to far! The hole in the multiplex doesn't have to be deep.
To prepare this thing for the next step, also drill holes in the direction of the top and bottom part. I placed the screws at a distance of 8cm from the side and from each other. For the holes I measured from the other end, giving me an offset between the two of 2cm.

Step 8: Glue the First Side Part to the Bottom

Now the glue is dried, we can start to glue the main frame together. The backside gives us some kind of support for this, because we want to have a box with 90° angles. Everything else will look like rubbish.

Get all the parts ready and start adding glue to the bottom part and the edge of the side part. Let it dry a few minutes then get it together. Do this in the upright position, with the front side down.
Now adjust the two parts, that the edges are really smooth and then put the backside on top. Drill through the first hole of the back side a little bit into the side part. You remember, the screws had 2.5mm and the drill is only 2mm, so there is enough wood retained to give a good strength.
Fix the back with the two outer screws to the side plane. Then continue with the bottom part and also screw the back to the bottom part. Make sure the parts don't move while screwing!

Now you can carefully lay it on the bottom and start screwing the inner rectangular block of wood to the bottom.
The back side, fixed with 4 screws, makes sure that we really maintain a right angle between the two parts.

Step 9: Glue the Second Side Part

Now add glue to the edge of the second side part and the bottom. Let it dry a few minutes and put the two parts together. Make sure all the edges fit and then start screwing the back to the second side part. Start with the lower screw near the joint, then adjust the upper part and insert the second screw.

Then carefully rise it up and fix the blocks inside.

Step 10: Add the Top

Now add glue to the top edges of the side parts and the inside of the top part. Let it dry a bit and then press it together.
Adjust the position and fix it with two screws on the back part.
Then turn it around, so that the top lies flat on the table. Then adjust the front end of the side parts and fix it with a screw. See picture three and four for this point.

Step 11: Add the Front and Finish the Back Side

When all parts are fixed you can add the front part. It only has screws in the upper half, so make sure to get it right. Don't use any glue yet, only screws.

Then finish the back side by inserting all the rest of the screws.
I suggest to first screw in all the ones in the middle and then the rest. Drill a bit with the 2mm bit to make it easier to insert the screws. Make sure you adjust any deviations before drilling and screwing!

Step 12: Glue the Front Panel

After all the glue from the last few steps has dried (24h), start to glue the front part. First unscrew the front part and mark the middle of a side.
Now apply some wood glue to the lower half of the front face and the frame and press it together with the help of something heavy, like water bottles or books. Make sure you don't load it to the middle of the front plate, because this will bent the sides up and buckle the front side. Alternatively turn the box around and load the back with something heavy or use supporting boards.

Step 13: Add Some Case Legs

This is the last essential step before you can play your Cajon.
As case legs I used some rubber devices I found at a hardware supply shop. They are either used as case legs or as a pad for doors to protect the wall.
Just screw them in the base plate at a sufficient distance from the edge.

Step 14: Add the Snare Wires

When you got here, you already hold a working Cajon in your hands! Plug it in and see what's happening.
No, I'm just joking, there is nothing to plug in, you hit the upper front with your flat hand and make nice noise. If you want to change the sound you can install some snare wires, but this step is optional.

The snare wires give a metal sound to the drum. If you don't know if you would like it, go to a music shop and try out some Cajon with and without snares.
Cut the snare wires in half and mount them on a small rectangular block of wood, then screw this to the top so that the snare wires touch the front panel from the inside. If you screw it close to the front the sound will be very hard, else the sound will rather be soft. Try it by yourself before finally fixing it.

Step 15: Fixing the Snare Wires (optional)

In the pictures you see how the snare wires on the block of wood are screwed to the top plate of the cajon. The snares are bent so that more than two third of the length touch the inner side of the front face. This gives a nice snary sound for the bass and nearly no snare sound for the high taps.

Step 16: Fixing the Snare Second Version (optional)

Meanwhile I built a second cajon and had to take other snares because the old ones were sold out and I didn't want to wait. Now these snares are more rigid than the others and fixing them the same way resulted in a very dull sound.
So I used a longer rectangular block of wood and fixed it with two wooden 'u's like you can see in the picture. By adjusting the height and the angle that the snares touch the inner front face I could adjust the sound of the snares.
With this setup I have a clear bass, a snary middle sound and a rather clear high.

Step 17: Finalizing the Cajon

The last  step is to grind down the surface to a smooth touch. You can do it by hand, but I suggest you use a grinding machine for the job. It's much more comfortable. Take 3 different grinding discs with roughness of 80, 120 and 240. Start with the 80 disc. This one is very rough and will grind down a lot if you stay to long on one place. Move over all sides uniformly.

If you finished the whole cajon, wipe down the dust with a dry cloth and then with a wet cloth. Let it dry completely before entering the second grinding cycle.

Now take the 120 disc and grind all over again. Do the same wiping as before and repeat everything finally with the 240 disc. This one is the smoothest and the surface should be really smooth afterwards.

Now you could paint it over or apply some wood conservation stuff. I used wood wax, because it is natural and gives a nice stain to the boards. Just follow the advices that come with your product.

An now you are really done with the job and can finally play your own cajon.