Start by cutting a 6 inch round circle out of inch thick board. Then cut a 3 1/4 inch circle out of the center. Sand the "O" and the center disk. You can even route the edges lightly to make it look prettier.
Now comes the fun part. Go down to the Home Depot and go to the plumbing section. Borrow a hammer and go around the store tapping on various kinds of pipe or tubing in various sizes and shapes, especially the metal tubing. Also, try out tubing in other departments like electrical or home decor. Find something that makes a beautiful sound when you strike it.
Get yourself about 8 feet or so of tubing depending on how ambitious you plant to be with your chimes. Get more if you tune them because you WILL make mistakes. If you use a larger diameter tubing than an inch or so, you may need to make your "O" ring and center disk proportionally larger.
The most important thing at this point is to cut your tubing the right length. Use a band saw or saber saw with metal cutting blade. The first piece is something of a crap shoot. Make it about 15 inches or so. Drill a pair of holes opposite each other about a quarter inch from one end of the tube, then suspend it with fishing line. Get the heavy 80 pound line if you don't want to replace it a lot. Mono-filament deteriorates in sun and weather over time.
Now that you've strung your tube, strike it with a hammer or hard object and make it ring. Set up a keyboard or other musical instrument next to it and try to find the note that comes closest to that of the tube. It probably won't match exactly. Pick the note on the keyboard that's just higher than the tube when struck. Now use your saw to shave off the end a little. No more than an eight inch. Restrike the tube and see if you're any closer to the note you want. Keep shaving till it's in tune with the instrument.
Now you need to pick out either a chord that includes that note or a line of music that includes that note. I have a chime that, struck sequentially, plays the seven note opening line from the Harry Potter theme. It makes a wonderful sound on a breezy summer day. If you want to do something like that, pick out the notes and then cut a tube to match each note. Just make sure one of the notes, preferably a low one, matches the tube you've already cut. You may have to try the tune in several different keys to get the right one.
The first time you do this, as I said, have some extra tubing on hand because you will mess up. Start with the low notes first because if you cut them too short, you can always recut for one of the higher notes. When you are done, try again to cut one to match the low note. Keep going till each tube matches a note in the tune or the chord you've chosen.
Now cut pairs of small holes for the monofilament line, 3/4 inch apart, with each pair evenly spaced around the "O" ring. If the tune or chord you chose has four, six, or seven notes, you'll need to figure 1/4, 1/6, or 1/7 of the distance round the ring to set your pairs of holes. String fishing line, through the holes you drilled near the tops of the tubes, then loop them through the pairs of holes in the "O" ring and tie them off.
Now drill 3 eighth inch holes evenly spaced in the "O" ring. Tie keeper knots in three foot long pieces of cord, thread them bottom up through the "O" ring and tie them together to a hook about six inches above the "O" ring. Tie a cord to the hook and drop it down the center of the "O". Drill a hole in the 3 1/4 inch round disk and thread it onto the cord. The disk should hang about a third of the way from the bottom of the shortest tube. Tie a keeper knot and then tie a flat thin piece of wood at the bottom below the tubes. It can be any shape you want, but light enough for the wind to blow it around and cause the disk to clang off the sides of the tubes and heavy enough to move the clapper disk.
Now all you need to do is hang it somewhere you can get a breeze and listen to the music. Minor chords are really nice for that ethereal kind of sound. Major or major seventh cords make for a cheerier sound. Piddle around with the placement of the notes to match how the disk tends to swing and you can have the chimes almost play a tune.
If you would like to do the tube cutting mathematically, there is an in-depth article that tells you all you need to know to figure tube lengths mathematically at Chuck's Chimes. And boy howdy is Chuck thorough. If you can handle college algebra you should be able to keep up and theoretically you could cut any tune you wanted out of any pipe you'd like and only have to cut once. He also tells you where on the tube to drill the holes to suspend it. Apparently there are nodes along the length that provide the best tone if you hang the pipes at that point.
Take your time and have fun with this project. Keep track of tube types and lengths from successful projects so you can repeat the set. Soon you'll be making wind chimes that are so beautiful all your family members will want you to make them for Christmas.
Then, again you may want to tell everyone you got them from a flea market in Kentucky so you don't have to ever go through all that work again. Depends on whether you enjoy building chimes or not.
If you're interested Chuck's Chimes also has this really great Wind Chime Tubing Length Calculator for tuning to a four note chord. Very nice.