I have been doing some research on how to make kydex/boltaron sheaths, and I was invited to share what I had found.
My perception may be different than yours, because I have seen a good number of sheaths being made by a local knifemaker, so my main goal was finding tips and tricks, and ways to do this on the cheap, and I found the following information helpful. Maybe you will too.
My favorite, why, I don't know... Maybe it was because it was my first...
http://usualsuspect.net/forums/showthread.php?t=69130 but you have to be a USN member (hint - just register :)
In the vein...
Not for knives, but, thermoforming is thermoforming....
Not my favorite style of sheath, but a bunch of good information. And a great tip for use of small clamps.... you will have to read it to find out.
Again, not a style I like, but informative.
And a word about searching.... I found some of my best results with a Google image search for 'kydex press', then when I found images that looked promising, I would check out their context. In fact, I just went further with that search and found the following threads and such....
Of course, you also sometimes get some goofy stuff too, which is probably part of the fun. I won't mention what I found...... but creepy....
Oh, and a few observations of my own....
Knife Kits sells a 'hand setter kit' whatever for hollow rivets, I have no idea how these could actually work, so I have an arbor press and flaring dies on their way to me. If you should decide to get the 'hand setter' things, try Tandy Leather, they are called something else but are 4 times cheaper if memory serves. I tried to use the 'hand setters' and it was a flop, nor could I imagine how they could actually function, and I have quite an imagination. YMMV
Anyone want my really overpriced things that don't work???
One of the tutorials listed above mentions using gardening knee-pad foam, for press foam. I tried this, and maybe my foam is different, but I think that the foam would melt a bit much over time, which in time could create patterns that you would be pressing into your work. Just something to consider. I am still using the gardening knee-pad foam, but I have also ordered foam for this purpose, specially marketed for this purpose, from Knife Kits.... We shall see.
Kydex is one material. Boltaron is another material, which is often marketed as Concealex. One material is pvc based, the other is acrylic, I don't remember which is which. But both thermoform, and about the only way you can tell the difference is that Boltaron is a bit stiffer, and has a different surface texture. Spyderco has been using Boltaron for quite some time, so that may provide you with an example, if you have one of their fine fixed blade knives.
Zip ties, yes zip ties are a fine substitute for rivets, I found this out when I had to modify a pretty badly made sheath to get it to work the way I wanted. I have used them from the hole to the edge, or even from hole to hole, like stitching.
Well, all for now, I hope you found this useful.