Guys,
I've been doing kydex for a while. It is really easy to learn, and doesn't take alot of expensive equipment to get started. Here is a link to Texas Knifemaker's Supply. Click on the word KYDEX under K. When just starting out, I recommend using the rivets numbers KYDEYE1 and KYDEYE2. These are pre-split rivets. The only thing necessary to set these rivets is a center punch and a small ball peen hammer. Real easy. The best kydex to start with is the black .060 Kydex Sheath Material, number KYDEX1, also on this page.
http://www.texasknife.com/store/s-pages/TKS_MainframeStore.htm
I recommend making a pattern out of paper first. I prefer one piece fold over sheaths to start with. Make the pattern big enough so you leave plenty of room for the kydex to form over your knife. Tape your blade with masking tape, then put your knife inside the pattern and trim until it fits the way you want. Make sure to leave enough room along the edge for your rivets and belt hardware.
Cut the kydex to the shape of your pattern. Tin snips work if you don't have a band saw. Put on a pair of good gloves, and use a heat gun to heat your kydex until its soft and floppy (another method is to stick it in a toaster oven set at 300 deg for a few min. but watch it closely!). Put your knife inside the kydex and fold it over. Use your gloved hands to mold the kydex to the shape you desire. If it gets hard, or you screw up, just simply reheat the kydex until its soft again. Making a fish mouth type opening adds a nice look to your sheath, and makes it easier to resheath your knife when you're wearing it.
Once hard, mark out where you want your holes to go, including the belt mounting hardware, then drill them out using a slightly oversize drill. Put your rivets through the holes with the finished edge facing out, and set them from the rear using a wide angle center punch and ball peen hammer. Use the ball peen to fully seat the back of the rivet. Just a tap will do. These are made out of painted brass, so they form very easily.
Pack the opening of your sheath with toilet paper or a paper towel (to keep the junk out), trim to size, then sand the edge of your sheath to the finish you desire. Last thing, mount your belt hardware. Before you put your untaped knife inside the sheath, I recommend blowing it out with compressed air and/or washing it out with hot water. Its not the kydex that mars up your finish, its all the dirt and gunk that gets trapped between your sheath and the blade.
I'll post a pic of a simple fold over type sheath. For more expamples click on the link to my website below, and follow the links to Available Knives. Lots of sheaths to look at there.
Hope this helps. Any questions feel free to pm me.
Scott
p.s. Sometimes, after installing the rivets and belt hardware, you'll find that the sheath fits too tightly, or maybe the knife won't go in at all. Simply heat your sheath up until it just gets pliable, open the mouth slightly with your gloved fingers, then gently push the knife into the sheath. Rock it around slightly. Again, use your fingers to shape and mold your sheath to the desired shape and fit. I prefer my sheaths to grab a knife's bolster, guard, or grip rather than the blade. This makes it less likely to mar the finish on the blade after repeated (dirty blade) re-sheathings.