There is no way around it; cymbals can make or "break" (lame pun intended) your career as a drummer. Cymbal care not only keeps your cymbals looking spiffy, but helps reduce the chance of them cracking and breaking. For tips on cymbal care, check out this instructable.
But if you want to try to fix your cracked cymbal or do something else with it (like make an effects cymbal), hopefully this instructable will give you some good ideas on how to do so.
Also check out some of my other drum instructables:
Effects Snare Drum
Step 1: Once it is cracked
If you are lucky, you were smart enough to shell out the extra cash to get a decent maufacturer's warranty when you bought your cymbal, and hopefully it is still valid. If you arent sure about your warranty, contact the store you bought it from and keep your fingers crossed. Its a great feeling to hand someone your cracked cymbal and get a shiny new one back. If you arent lucky enough to have your cymbal under warranty, keep reading.
If you can catch the crack early, you basically have three choices:
Try To Stop The Crack:
Think of this like a major surgery. You can get lucky and perform a good fix, retaining most of the acoustic signature of the cymbal and keeping it from losing its sound. However, if done improperly, trying to fix the crack can end up dramatically altering the sound of the cymbal. Sometimes, though, you have no other choice.
If you have dealt with cracking cymbals before, you know that your cymbal has entered a new stage of its life. If you are able to accept this, you can try to do something interesting with your cracked cymbal, and make some good out of a bad situation.
Live With It:
Depending on the way you play, it can take a while for a tiny crack to turn into one that destroys your cymbal. If you dont have the money to go out and buy another pricey cymbal, and you dont want to take the chance of further screwing up your cymbal by trying to fix it, you can just deal with it and enjoy it while it lasts.
Step 2: Fixing a Crack
One of the most commonly suggested methods for repairing a crack is to use epoxy to seal it. Try to force the epoxy into the crack without making too much of a mess. If you get too much extra epoxy on the outside of the crack, just wipe it away with a damp paper towel. After the first application, lightly hit your cymbal with a stick to get the epoxy further into the cymbal. Apply more if necessary. Depending on the type of epoxy you are using, you may have to put it in an oven to dry it, or just let it sit out. Once it is dry, you can polish the cymbal to further reduce the roughness.
My opinion on this method is that it should be used as a last resort. My experiences with using epoxy were mediocre at best, and it pretty much ruined crash cymbals that I tried it on. Give it a shot if you dont want to drill. Otherwise...
Drill a Hole:
This may be your best bet to fix cracks of all kinds and all sizes. You can drill a hole or holes at the end of your crack to keep it from spreading. Try to use the smallest bit possible, but make sure that the hole is bigger than the width of the crack. Make sure you get a drill bit for metal, like one of these.
Once you have drilled the hole, you may notice a buzzing sound when you strike the cymbal. If this is the case, use a small file to file down the edge of the hole and the crack. Keep in mind, if you are doing this on a lathed cymbal (one the has tonal grooves or ridges on its face), drilling holes on these ridges can obliterate whole ranges of overtones from your cymbal's sound, but sometimes you have no other choice.
In the case of a small crack or chip right at the edge of a cymbal, I have heard of people trying to use a lathe to cut away at the cymbal's bearing edge, effectively reducing the diameter of the cymbal past the edge of the crack. It should be noted that not only will this immensely effect the sound characteristics of the cymbal, but is extremely dangerous. You probably shouldn't attempt this method unless you know a metalworker.
A drummer friend of mine had a really nice Paiste 2002 ride that was developing a crack horizontally along its bow. He didnt want to do anything too evasive, so he used standard solder to try and 'weld' the crack shut. This worked pretty well since the solder is much more similar to the metal make-up of the cymbal than epoxy. It kept the crack from spreading and didn't sound so bad, but he had to re-solder it just about everytime he played. Check out this instructable on soldering if you need some tips.
Step 3: Getting Creative
This is a good option if you first try to repair your cymbal by drilling holes. If you did this and you didnt like the sound that your cymbal had, you can try to insert rivets into the hole to create a sizzle effect. Some cymbal companies sell their own rivets that you can use, otherwise, find a riveter. If you dont have the means of using a riviter on your cymbal, you can put together a make-shift rivet by putting a small nut and bolt through the hole. It may look ghetto, but it will sound similar to the many riveted cymbals that the name brand cymbal manufacturers make. If you get ambitious, you can drill more holes to install lots of rivets.
Cut a New Cymbal
If you go to a drum store, you might notice many of the $100 bells that seem to be nothing more than the bell of a cymbal without the bow on it. That is, essentially, what you can make. Using a pair of metal cutters, you can trim down the cymbal until only the bell remains. These actually dont sound half bad, and can make a good combination when stacked with a splash or china cymbal. If you have access to a lathe, you can use it to smoothe out the rough edge of your new bell.
You can also experiment with other designs, cutting your cymbal into various shapes and sizes as you try to find a cool sound. Try making a ribbon cymbal like the ones below by cutting spirally along the bow. Just be careful, the edges of your cut cymbal can be sharp and brittle.
If you try to fix or get creative with your cymbal and you end up just hating the way it comes out, a final option is to use a pair of metal cutters and make a bunch of brass guitar picks. Just use a guitar pick as a sort of stencil and make a bunch to give to your guitarist friends, or even sell them on ebay. Thanks to Quarry for detailing this in his instructable.
Step 4: Avoiding Cracks
Always use felts and sleeves:
It is never adviseable to use a cymbal without properly cushioning it at the bell. You can never use too many felts, and it is definitely worth shelling out the few dollars it costs to picking up a few of these. Just as important is using the plastic sleeves to keep the inner edge of the cymbal from making direct contact with the metal of the stand. A common type of cracking, known as keyholing, occurs when plastic sleeves are not used and small cracks appear while the hole begins to lose its perfectly round shape. Also, cymbal springs like these allow the cymbal to vibrate without applying too much tension.
Clean and Polish:
Cleaning your cymbals keeps the surface from degrading. The oil from your hands easily rubs off onto your cymbal, and overtime your cymbals can rust. This not only effects the sound of your cymbals, but it can increase the likelihood of a crack happening. You can read more about cleaning your cymbals on this instructable.
Know How To Hit:
The best way to avoid cracking your cymbals is to know how to strike them. There are a lot of factors here. If you are a heavy hitter, buy heavier cymbals. It just isnt too smart to buy thin crashes if you play metal. Stick choice is important too. If you're using 2Bs or something thicker, be more careful when you hit a thin or light cymbal.
Most importantly, however, is your stroke. When hitting a cymbal, you dont want to strike the edge straight on, but you dont want to hit it right on the bow either. It is best to try to strike with a glancing motion, moving your arm slightly to the left or right during your stroke. This will help you avoid cracks and should produce a more articulated sound.