We bought a cheapo wooden xylophone from Target and the pitch of every single bar was off -- and we're not talking off by a little bit, we're talking off by full pitch steps in random directions. So I set about making my own. I made it at TechShop San Jose (www.techshop.ws) with my wife. It was both of our first time in the woodshop, so I can guarantee this is easy to make, and it took ~2-3 hours but it would take an experienced hand less time.
TOOLS NEEDED: We only used:
2) Belt sander
3) Drill press
However certainly some of the steps would be better to do on better designed tools (e.g. the first cutting step may be better on a table saw but we couldn't get the fence close enough to the blade, so ended up using the bandsaw).
* Two 1 inch square, 3ft long rods of a hardwood. If you can get it in rectangular cross-section that is about twice as wide as it is thick, then you can skip the first step, where I cut the square bar to make two rectangular bars.
Note: Use the hardest wood available. We used poplar, which is harder than pine but not amazingly hard. It's good enough though. http://en.wikipedia.org/wiki/Janka_Wood_hardness_rating. Harder woods makes the sound ring out for longer, which is why metal "xylophones" (actually metallophones, since "xylo" means wood) ring out for longer than wood.
Note 2: You'll notice the frame wood is redder than the wood that makes up the xylophone bars. In reality we were going to make the whole thing out of poplar but then found some scrap redwood the right size, so decided to use two different woods for the contrast.
* Wooden pegs. You can either get pegs shaped like the one in the photo, that look kind of like a nail, or get wooden dowel and make your own (by attaching a wooden ball to the end of a dowel, for instance). You can get the pegs shown from a hardware store. The ones we used had a shaft of about 3/16" and shaft length of about 3/4".
Note: Alternatively you can suspend the blocks on strings or rubber bands as described later. We used pegs because we wanted something robust for young children to throw around without the bars falling out.
* A wooden dowel and wooden ball to make the mallet. Really any size will do. We used 3/16" dowel about 8" long and a 3/4" diameter wooden ball. Drill a hole in the ball, put some glue in the hole and put the dowel in it, and you're done. See the third photo above.
OK next we make the xylophone itself.
Step 1: Making the bars
Cut the square-cross-section wood lengthwise to make two rectangular cross-sections. We cut each 3ft length lengthwise. One of these 3ft lengths is shown in the photo after we cut it. Just make sure you make the two sides as evenly thick as possible, so your pitches are on. You'll be tuning it later anyway but you should still try to do it to make life easy for yourself.
We used the bandsaw with a fence to keep it the same thickness all the way along. See photo. Then we sanded on the cut side. We were left with two rectangular bars per starting square piece.
Next you cut the bars to length.
HOW TO CHOOSE THE LENGTHS:
Get the lengths from the .xlsx file here: davidnhutch.com/files/keep/XylophoneLengths.xlsx. I found some xylophone bar length calculators online (link is in the .xlsx file), and used that as a starting point for the Excel file. Basically, you input the total length of rectangular bar you have available and it will tell you how to cut 8 bars that use that length, making an octave of musical notes. These won't be perfect so we will tune them later, but you should try to cut them as accurately as possible anyway.
* Larger bars are better. Larger bars ring longer, make better sound, are easier to tune (because shaving a few mm off a larger bar does little while shaving the same amount off a smaller bar does a lot). However you don't want to go too large otherwise: (1) your wood may be warped and this will show for longer bars, (2) It may be too big for use by small kids, (3) Many of the wavelengths of sound may be below human hearing. I recommend keeping the bars less than 12" long, and for a small kids' xylophone a longest bar of around 7" is fine.
OK now you have your bars cut. Drill holes that are 1/4 and 3/4 of the way along the bar as shown. The holes should be much bigger than the shaft of your pegs (perhaps 1.5 times larger diameter), because the bars need to be able to freely move.
Next we will make the frame, then the suspension padding, then assemble it and we're done.
Step 2: Making the frame
I suggest you just lay out all your bars how you want them, then cut the frame by eye so it is any length longer than the lines of holes in the bars. The size of the frame really doesn't matter aside from needing to be longer than the lengths of the bars. As you will see later, the frame is a trapezoid but getting the angles on the ends doesn't matter either for now -- just make everything longer than it needs to be.
OK, you can make the frame in a number of ways. The way we decided to make it was to cut a slot into the end of each long frame-edge using two parallel cuts of the bandsaw. Then make the two short pieces thinner so they fit in the slots, again by pushing it against the fence of the bandsaw and cutting a smaller thickness. Be careful here as you are cutting small pieces so don't get your fingers in the saw, use a "push-stick" for everything.
OK, now you have two long frame-edges with a slot in each end, and two short frame-edges that slot into the slots. It's really ugly at the moment because everything is sticking out past where it should, as shown in the photo. That's ok, we'll clean that up in the next paragraph.
Once the whole assembly is how you want it, and will lie under the lines of holes where the pegs will go into it, then glue it all together (just put some wood glue in the slot and slot it together, and let it dry a few hours.
Next take the whole frame to the belt sander and shave it until everything lines up as shown. It will look like you made it that way with careful and precise angled cuts! Notice how ugly it was before to how clean it looks now (see photos).
Step 3: Assembling it
Now, as we have seen, the bars will make some sound if hit with the mallet while they are just laying on the frame, but this sound will be better if we use some foam to "suspend" the bars above the frame. Cut two strips of thin foam as shown and make holes in them that line up with the holes in the frame. put this below the bars, replace the bars, and re-insert the pegs.
Once you're entirely happy, glue the pegs into place.
Note that you can suspend the bars using rubber bands, as in this copper pipe glockenspiel:
However this is not a good option if this is for younger kids who may easily destroy such a delicate setup. The peg approach may also be broken (resulting in small parts which can cause a choking hazard -- but this is a risk you take on yourself), but is less likely. And besides, all-wood looks better :)
Lastly, you can paint each of the bars a different color. We don't have any paint so will do that later, but here the design is entirely up to you!
Voila! A toy xylophone that actually sounds a LOT better than our cheap one from Target!