If you have a perfectly good guitar you would like to ruin, one good way to do so is to remove the frets. You could remove them with a hammer and a screwdriver, but that's a far too quick and easy way of ruining a perfectly good guitar. Here's the operation I recommend based on my experiences with de-fretting an Alvarez ATK250 5-string bass guitar.
Here are some things you will need:
First, remove the strings from the guitar. You can set them aside for reuse, but you might as well take this opportunity to install a fresh set.
The actual fret removal is the tough part, which is why we have the band-aids on hand. Guitar frets are normally barbed chunks of metal not entirely unlike razorblades and tend to be glued into place in addition to being held in with their barbs.
There's no easy way to overcome the anchoring barbs, but the glue can be defeated at least partially by heating the frets using a soldering iron to weaken the hold of the glue. It may take a while to heat up the frets enough to make a difference because they will act like one giant heat sink.
Once you have weakened the glue, take your screwdriver or chisel and gently pound on the edge of the fret in order to knock it free from the neck. The danger here, other than self-mutilation, is that the barbs of the frets will tear chunks of wood from the fingerboard as they are ripped free. To a certain extent this is usually unavoidable, but proper care should minimize the destruction.
After the frets have been removed, sand the fretboard evenly. Use the rough sandpaper first and then the finer paper. You shouldn't have to sand the fingerboard down much, just enough to get it fairly smooth and even.
After the fingerboard has been sanded down, use the polishing cloth to apply the tung oil. It is applied much like a wax or varnish. You may want to apply more than one coat, but one well-applied coat should be sufficient. Tung oil tends to be pretty sticky and messy if not kept under control, so you'll want to do this over some newspaper and try not to get any on you.
It's usually best to let the tung oil dry overnight. It will harden the fingerboard and give it a nice pretty finish, even filling in some of the rough spots from the fret removal. If your fingerboard is in particular need of help, a second coat would be a good idea. The protective coating should extend the life of your fingerboard since the strings will be rubbing directly against them.
Restring the guitar. Round-wound strings are reported to sound the best, although they will be the hardest on your fingerboard. Half-round or flat-wound strings are recommended for guitar life, but if you just ripped the frets out of a perfectly good guitar you're obviously not concerned about guitar life. Use the round strings.
The most important part of playing a fretless instrument is being able to play in proper pitch. If you haven't had ear and pitch training, now would be a great time to sign up for some.
Enjoy your freshly-ruined guitar!
- Xangis