KYDEX Sheaths

Click on any of the thumbnails below for a more detailed photo




KYDEX is one of the new wonder plastics that is impervious to water, ultraviolet,  solvents, the elements and almost all alien death rays. It's a thermoform or heat moldable sheet which makes it ideal for home made knife sheaths. And since it's pretty tough to carry a bowie knife in your back pocket, you are, in all likelihood, going to need a good sheath.
Here's a quick overview of a pretty basic knife sheath. Modify as needed to fit your knife and design considerations. Plan ahead and lay it out before you start to cut or form. I'll cover the basics here, but every knife design is going to have it's own requirements. Lay it out on paper first if you want to try out different ideas.
You'll need to start off by making two jigs to mold the front and back from some scrap wood that you more than likely already have laying around.  The jig to mold the back simply has a step to form the lip and shoulder on the back of the sheath. This step should be about 1/32" more than the thickness of the bolster.
The most convenient source of heat to soften the KYDEX comes from a heat gun. This will give you a lot more control than trying to soften the sheet in an oven.  I like the smaller nozzle  and the higher heat that the Ungar provides, but the paint stripping heat gun from Black and Decker works fine. Check Ebay ; you should be able to pick one up for 20 bucks.
I use cheat lines drawn with a silver pencil to keep me oriented, and tape to keep the sheet from moving on the form while molding. Move the heat gun back and forth  slowly until the KYDEX starts to soften and get rubbery.  ( And, yes, I did melt a spot on the carpet. Yike! Learn from this! )
When the KYDEX is soft, I use a scrap piece of wood to force it into place to get a good square  lip on the back of the belt loop. Hold it for a minute of so until the KYDEX cools and hardens 
Use the same technique to mold the shoulder that will sit against the bolster of the knife
Use the heat gun to soften the top of the belt loop . The silver pencil lines tell me where the bend should occur and where to concentrate the heat for softening. The scrap piece of 1/4" plywood will provide a good sharp corner to bend the belt loop around.
When the KYDEX is softened, flip it over, using a scrap piece of wood inside the loop  to help hold it in shape until it cools. 
To make the jig to mold the front of the sheath, you'll need to make a wooden copy of the blade just a hair larger than the blade itself. The KYDEX will be molded over this. You'll also need to cut out a profile of the knife about 1/8" larger than the blade, cut out of 1/4" scrap of plywood. 
Tape again is used to keep the sheet from shifting. The silver pencil lines will help align the plywood cutout and show you where to concentrate the heat.
When the KYDEX is softened, use the plywood cutout to force the sheet over the wooden copy of the knife blade. Hold it here for a minute until the sheet hardens. 
I use a few drops of super glue to hold the front and back of the molded KYDEX sheet together temporarily until I can get some rivets in . Notice the fancy clamping system. Hey, it works. 
Drill a few 1/8" holes for the rivets.
Use the rivet set tool and anvil ( both usually available with rivet sets at any leatherworking or craft shop) to attach the rivets. 
I use my bandsaw to cut off all of the excess sheet and get the sheath into the final shape. A simple rubber eraser will get rid of all of those silver pencil lines. Touch up any rough edges with 180 grit sandpaper. 
With the knife in the sheath, I soften a small spot on the front and push the KYDEX tight against the blade for a good, tight, custom fit. The knife will now feel like it just "Clicks" into place. 
Hope you like black. Yes, KYDEX does come in other colors but the composition seems to be different enough that it's not as freindly to work with.
Here's a drawing for a slightly more advanced custom KYDEX sheath using the same techniques that we just ran through.  This design covers more of the knife and part of the handle for a very secure carry. Since these are custom sheaths, every one you make will be different depending on the knife.