Kydex - all created equal?

[double gun]

I’m a hobbyist who occasionally uses kydex for sheaths. I’ve always bought my kydex from Tandy leather to avoid shipping fees, but recently I started to wonder if theirs (Tandy’s) is the same as other suppliers in regards to quality and workability.

Not sure if kydex is a brand name or just the type of plastic. Or if there is a better product I just don’t know about.

Thanks in advance for any and all info

 

[David Mary]

Kydex is a brand name for a specific type of thermoplastic. Boltaron is another one, with a higher tolerance to heat, and thus better suited for sheaths that will live in hotter climates, but I can't find it in as many colors as Kydex. It is also less prone to melting and gooping off during grinding, making it nicer to work with. Some have complained that it ripples like bacon when heating it prior to pressing, whereas Kydex doesn't. I had that problem when I first tried heating Boltaron in my oven. I don't have that problem with my new process which is to heat it on a pancake griddle, with a board over top. Wax paper underneath, and the board has a bit of clearance so it doesn't actually touch the show side of the material, but it keeps the heat in so the material heats evenly, and I think this is why it doesn't bacon up on me. Boltaron is my principal sheath material. Holstex is another, and more similar to Kydex in its properties, but seems to be available in many colors, and also some interesting textures like raptor skin, basketweave, twill, and maybe more. I typically get my Boltaron and Holstex at CKK. I can't remember the last time I actually bought Kydex.

 

[double gun]

Thank you so much for all the information.

 

[David Mary]

You're very welcome. Good luck and don't forget to show us what you make!

 

[Taz]

I've tried Boltaron in the past and hated it because it felt more brittle to me? Its older CF pattern stuff and felt very plasticy and brittle and seemed to want to melt more when heating. I havent tried it lately with my better equipment, so I will order some. I like the more matte finish on the kydex and Holstex better. The Boltaron I tried was very glossy too.

I use mostly Holstex now unless I need to use a particular pattern/color I can get in Kydex. The Holstex seems to form better for me, and is easier to adjust retention level wise for me than Kydex is.

 

[David Mary]

Kydex is definitely is more "bendy". If you don't score it perfectly, when you try to snap it, it will just bend a bit at the spot where you missed with your knife. Boltaron, on the other hand, is more liable to snapping outside of the score mark. But if you score it with a ruler, and make sure to wiggle the outside corners back and forth a bit first, and then carefully build pressure along the score mark, you shouldn't have an issue. And once the sheath is finished, it should be more than durable enough to withstand any forces you'd expect a knife sheath to be subject to. I have messed up a few sheaths over the years, and used them as opportunities to destruction test them, and still have every confidence in Boltaron.

The higher heat tolerance of Boltaron may require you to prolong the heating step of your process a bit more, or crank up the heat a bit. I remember reading that about 30° F more for Boltaron than Kydex was recommended. But now the dial on my griddle just kinda lives at around 400° for both Boltaron and Holstex, and once the material "feels" ready to form I grab it. I don't do a whole lot of blocking, but I fine tune the mouth of the sheath and thumb ramp with a heat gun and my fingers before the final grind to shape.

 

[Taz]

Good to know! I think when I tried it many years ago, I was using a heat gun to heat it and some foam glued to boards in a bench vise for my press, so it could have been a lot to do with my method as well!

I usually do one layer of blue painters tape, one layer of gorilla duct tape, and another layer of blue painters tape on each side of the blade before I mold it. I find that I get less scratches with the Holstex versus the Kydex with the same method. I believe the Kydex forms a little bit tighter to the shape of the knife and sometimes I get scratches just above the edge Bevel with a Kydex sheath, but the exact same process in a Holstex sheath doesn't have nearly as much scratching problem.

 

[David Mary]

The struggle is real. One thing to look at might be slightly increasing the distance of your eyelets from where the edge of the knife rests in the sheath. The tape you use sounds good. I use five layers per side of painters tape for just about anything under nine or ten inch blade length.

For taco sheaths, I take chamfered piece of G10 and run it through the sheath a few times to remove debris, then a worn 220 grit ceramic belt strip, folded in half, and run that through a few times, and finally, I place a 1/4" thick G10 wedge inside the sheath to hold it open, making sure that it is only contacting below the top of the eyelet line (so it doesn't trap debris inside where the knife will contact) and spray it out with fast running water, as fast as I can get with a combination of water pressure and my thumb on the faucet (at least in winter, I just use the jet mode on the garden hose when it's above freezing - yes I have to do this outside and it royally sucks in the winter! ).

After that I place the sheaths in a plastic container that is kept clean and dust free where the sheaths will wait for their turn to have eyelets installed.

That's actually what I have to do next, after I do the heat gun step followed by final profile and ergo clean up.

I'm really loving the horizontal groove on handles for sheath retention, and they are nice for grip too.

 

[Taz]

Good tips! I may try multiple layers of the blue painters tape. I used to just do 2 or 3 (for damascus blades) layers of the blue painters tape, but over the years, it has gotten thinner. Duct tape thickness varies with different brands, too, so I did some testing to come up with my layer stack. Damascus blades get an extra layer of gorilla tape to give plenty of clearance on the blade. The Gorilla tape sometimes leaves a sticky gummy residue inside the sheath though.

I do all of my drilling, countersinking and shaping (and started keeping the eyelets farther from the edge) and polishing and chamfering of the outside edges. I used to flush out with water and paper towels wrapped around a thin butter knife blade to clean the inside. I also usually use the back of a utility knife blade to make sure any kydex burrs are gone from the inside of the holes and the edges and then run some folded up 400-600 grit sandpaper through the sheath where the eyelets and seams are, but I started using Denatured Alcohol on paper towel instead of the water to clean the inside of the sheath out since it helps get rid of the tape residue as well as the kydex dust. Once it's cleaned and dried, I set the eyelets and then use the heat gun to tweak the opening to flare it and make sure the handle has good retention. I usually have a palm swell, and the front of the handle flares up (but the leading edge is rounded) a bit, so I have to open up the sheath opening for that and adjust the tension. For testing the retention and stuff, I remove the molding tape layers and do a single blue tape layer on each side of the blade so if there is any grit or rubbing, I will see it on the tape and not the blade! Once the sheath is done, I get it out of the shop, then sharpen the blade and do the logo, so it doesn't go back into my shop to get any more dust/grit into it. I drill drainage holes in the sheaths near the tip of the blade so it can be flushed out with water in the future.

This is a pretty typical handle shape for me, so I get lots of retention at the front of the handle. When I remove that front hump and have more of a coke bottle shape, the retention shifts to the finger choil area and I gotta make sure it has enough retention, but not too hard to draw. Puukko style handles are really hard to dial in the retention since there isn't really a guard/finger well/hump to the handle, so those get more of a tapered fit to the sheath instead of a snap/click fit.

 

[David Mary]

That looks very nice, and cool material! Cryptek I think they call that pattern? I haven't grabbed any yet.

How tall is that blade?

I tried duct tape on blades for molding, but decided against it since it seems to add extra work for me, especially in cleaning my EDC knife more often. Painters tape is cleaner and easier to cut, and never leaves any goop in the sheath.

You countersink your eyelet holes? That sounds like a lot of extra work. I just drill mine with a dull 1/4" drill, and then run it through the hole at an angle for a second, and my eyelets slide right in. The dull bit is because sharper ones (I use split point for everything) tend to grab the sheath at the tail end of the cut and want to make it spin. Didn't want to have to start clamping my sheaths down just to drill them, and the dull bit doesn't want to helicopter them.

I thought about paper towels, but I was concerned that they are not durable enough and will leave bits of themselves in the sheath. Same with the various shop towels I've tried.

 

[Taz]

Yes, it's Kryptek pattern kydex, its a popular choice and comes in different colors! The wood patterns are also cool looking, too.

The blade is around 1" or so tall; it's patterend off of a Benchmade Bugout, but this one is a touch shorter lengthwise.

I do the countersink by hand to basically get any burrs from the outside that may prevent the eyelets from folding over nicely. It's pretty quick to do! I try to use a brad point wood drill bit for the holes and I have my drill press slowed way down for metal drilling, so it's controllable and no helicopters!

Yeah, the DNA on the paper towel works nicely; I used to flush with water and then dry with paper towels, but it left bits behind even more and I always had a lot of dust left over and it took forever for the sheath to dry out (no compressor at that time to air blow it out). The DNA often removed the tape residue and dries quicker as well, but I am going to try multiple layers of painters tape. Gorilla tape is expensive!! I open up the sheath and blow out any particles I find after I wash it out with the DNA/paper towel. I use a small piece of paper towel wrapped around a thin metal spatula to get into the sheath; maybe the thinner spatula worked better than the slightly thicker butter knife I used before that made a difference?

 

[AbLonewolf]

Pretty do the same as most when it comes to taping the blade.

To avoid getting debris inside the sheath, I shove a piece of blue shop towel into the opening, and push it down with a screw driver. Eliminates grit going in by a lot. Once done, slowly yank it out with tweezers or small long nose pliers.

I use an electric griddle with a heat sensor gun to cook the Kydex. I think it works better that an oven.