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Kydex - Start to finish

Allegedly, most plastic suppliers have it available. Minimum purchases and other restrictions may make this unpractical for you. I’ve only used texasknife.com for mine. Their minimum shipping charge is such that I only place an order when I’m ready to get a number of things.

Choosing the kydex.

Kydex does come in multiple colors, patterns and textures. Precisely what is available depends on your supplier. Black is the one most widely available and seems to be what is most preferred. Various camoflage patterns can purchased too, or even a carbon fiber pattern. A slightly textured surface masks scratches and such better than a smooth surface.

Thickness is also an important consideration. Texas knife carries kydex in .09 .08 and .06 of an inch. Thicker sheets are tougher and stronger. Thinner sheets mold more easily and tightly. My very first attempt in kydex was in the .08 thickness. It formed nicely and tightly. But I soon learned that my 3/16 eyelets wouldn’t hold in two layers of that thickness.

And those eyelets were of too small a diameter for the chicago screws of my Tek-Lok.

I ordered some .06 kydex and have worked in that for the sheaths I have made since. With some deeper eyelets, I can also work in .08, but haven’t yet done so again.

Gearing Up

Reading up on the process, I learned I would need some tools. A heat source for heating the kydex is necessary. The home oven or aheat gun] are used a lot. Kydex stinks when it is heated. Use good ventilation.

Initial shaping of the sheet of kydex is most easily done with autility knife/box cutter. Score the sheet well and completely, then snap along the score, kind of like cutting glass.

To form the kydex, I’d need a . Eric Noeldechen (Normark) of On-Scene Tactical has a 2-ton commercial press for his excellent kydex. Reading up a bit, I found this very useful guide http://www.bladeforums.com/forums/showthread.php?t=287528&highlight=kydex+tutorial.

Knowing my taste in personal tools runs a lot smaller, I built my press smaller.
Press Fabrication

With a 12 x 12 inch square of 1/2 inchplywood board, I cut two 12 x 6 pieces. I lined that with 1 inch of foam. That meant I only needed one piece of foam as available from Texas knife supply. You could also use a few layers of closed cell sleeping pad foam for camping. Both work.

I attached the foam with hot glue. A spray adhesive would work well too.

That makes my press about 3 inches thick, thicker with the object in but unclamped. With that as a guide, I picked clamps for applying pressure. I use three clamps, two 12 inch pistol grip bar clamps and 1 four inch C-clamp. I initially used extra C clamps but have found this lesser combination fast and powerful. I’d use a third or fourth bar clamp if I had them instead of the C clamp but this works and saves me money.
With the bar clamps, I can quickly apply a lot pressure to the press at one end. Then I even out the pressure towards the other end of the press with the C clamp.

Shaping the formed sheath can be done a few ways. I use adremel with a reinforced cut off disk and sand paper. Normark uses a band saw. A coping saw would also work. I haven’t heard of any specific health risks from the dust, but protection is always smart.


Making a Sheath

You can make a kydex sheath in three basic ways: Folded over, sandwiched and flat.

For a fold-over, the knife is laid at the center of the sheet. The sheet is folded over the knife and pressed. Every commercial or custom kydex sheath I’ve purchased is in this style. I’ve discovered I prefer more mounting options than this offers me. There are exceptions of course.

For a sandwich, the knife is placed between two sheets of kydex and pressed.

For flat, the kydex is placed on a foamed press sheet, the knife then placed on the kydex and a flat rigid board is used for the other side of the press. This makes a sheath with one flat side and one formed side. The flat side is simply a sheet of kydex that you attach and cut to shape

Figure out which sheath style is best for your uses and design.
Examine the knife carefully. For best results, the knife should have a narrow spot somewhere, most often where the grip meets the guard or blade. When you form the kydex, it will form around and behind this narrowing, holding your knife securely in your sheath. To allow you to draw the knife, the kydex has to be able to deform or move enough under your drawing pressure to release the knife. This strongly influences the function of your sheath. Too much kydex behind the narrowing, or a rivet in the wrong place and your sheath won’t operate properly.

Trace your target knife on a sheet of paper. I usually use graph paper as that makes measuring easy. Now, draw your desired sheath around that tracing. Include rivets, eyelets, and screws and their offsets from edges and the knife itself in the design.
When you form the sheath, the kydex deforms around the knife. You need more kydex than your object is wide. Be generous. You can always trim extra as needed but you can’t add any kydex back in.

In my small knife sheaths, I’ve found 3 inch widths sufficient for a side of the sheath. For a fold over you’d double that, maybe more if the object is really thick. A flat style would need more too.

If you’re frugal, you don’t want to waste too much kydex in the project so some initial shaping of the raw kydex is in order. I prefer the method already mentioned of scoring the kydex and snapping it. A metal straight edge is critical in accurate shaping for making clean straight scores. A basic rectangle is all the rough shaping I do.

For sandwich style sheaths, there’s some added concern at this point. The two pieces when formed won’t stay together on their own (even though some stick a bit). The better the match between these pieces, the better the final sheath. So I rivet one end together, trying to place it so that it forms a useful point in the sheath. This keeps the pieces lined up all the time and simplifies some other steps as well. With a spring clamp or two holding the pieces togehter, I drill the rivet hole through both pieces at once. In goes the rivet and I flare it.

Heating the kydex

I prefer the oven to the heat gun. The oven has more controlled heat and is easier to prevent overheating, at least for me. The heat gun is faster.

Using the heat gun is mostly about developing a good motion technique to heat the kydex evenly.

What is the risk of overheating? If kydex overheats, it becomes brittle and shiny at even higher temperatures. Sticking is also attributed to overheating.

Heat the oven to 300 degrees Fahrenheit. Temps as high as 320 can overheat it I’ve heard. Most ovens fluctuate 25 degrees either side of the set temperature so there is some risk. Put the kydex in the oven. I put it on an inverted pan or a cookie sheet. Let it heat about 10 minutes or until limp and flexible.

Meanwhile, ready the press. Set the press plates up and ready clamps by setting their openings to fit over the full press but clamp down quickly. Have the knife handy as well of course.
When the kydex is ready, you have to work quickly. Remove the kydex from the oven. The kydex is hot but doesn’t conduct heat well. A towel or hotpad is enough to handle it.

For a fold over sheath, I fold the kydex as I remove it from the oven. The knife is inserted and quickly clamped. This can be a bit fussy. You may have to reheat it and press it a couple of times to get the fit you want. When you reheat it, the kydex will unform itself. The kydex seems to suffer from lots of reheatings. I often need two heatings and have done a third heating on two occasions. I did more than that once. That sheath was a failure.

For the sandwich sheath, the clamped end really helps. You don’t have to fuss nearly as much with lining up edges. It’s easy and tempting to center the handle by where it protrudes from the kydex. Don’t. You want to center the blade in the sheath, not the handle. Watch your tip too. You don’t want it too close to the rivet or off to the side. If your sheets are sticking together as you place the blade, they may be overheated a bit.
Similar issues would seem to apply to the flat style sheath as well.

Putting the whole knife in the press is hard on the foam, often making tears. I prefer to leave part of the handle out of the press when possible.

Cover, and clamp it up as fast as you can. Some advocate standing on it. That’s time consuming and any wiggles might cause problems. I prefer the clamps. I have other things to do with my time.

Five minutes is usually enough to form the sheath, though it won’t be cool yet. Ten minutes is better and safer.

Bar clamps tend to release a bit excitedly so be careful as they will jump and kick a bit on release, possibly marring surfaces below, such as your table or counter.

It’s common for the kydex to stick a some after clamping. This isn’t automatically a sign of overheating as the pressure and residual heat were involved.

Assess the fit and forming. Are the form lines crisp and distinct? How are the gaps around the blade? Where two sheets meet, there is usually a little gapping where the kydex bends together to meet. That’s OK, but you want them fairly small. Of course, if the knife has a gaurd, a larger gap is probably necessary to get the knife in and out.

Eyelet placement

Take some spring clamps or other clamps and approximate your eyelet placements with them. Test the knife for retention and release. The very first test may be tricky because the kydex may be stuck to the blade from the press. Be careful. Adjust clamp placement until you get the retention and release you desire. MARK the spot with PENCIL. If you don’t mark the spot, you will not know the exact best location. This is most critical for the eyelet closest to that narrow retention spot on the knife as was discussed in the design steps.

If you used a Sharpie, or pen, the ink probably won’t come off. The pencil rubs or wipes off easily so exercise care to retain your pencil marks.

You want the edge of your eyelet flare to come to the marked point. So mark the center point of the eyelet about 1/8-3/16 inch away from the pencil point as appropriate for your eyelet. Use a sharpie this time as you will drill this mark out of the sheath. With this point established, you can fine tune the layout of the other eyelets. As I use a small TekLok, my preferred spacing is 1 inch on center. If you need to make some layout lines to keep things lined up, use pencil. Mark all center points for drilling with the Sharpie.

For accurate drilling, you need to center punch each of those Sharpie drill marks. I use a 16d nail and lightly tap a starter hole for the drill bit tip to rest in. Otherwise, the spinning action of the drill forces you off the precise point to drill.

The size of the hole you drill depends on the eyelet, rivet or screw you are using. The size hole is usually specified on the package of eyelets.

When it comes time to drill, it’s best to drill both sides of the sheath simultaneously so everything matches. The problem is that when the drill clears the first side, the kydex on top climbs the drill bit and forces you off the mark for the second side. Before drilling, use spring clamps to hold the kydex together within an inch of where you are drilling. This is another time the pre-riveted layers of kydex in a sandwich sheath is useful.

Line the bit up in the center punched hole and drill through.
Setting the rivets or eyelets

A lot of the work of eyelets is getting the darn things in the holes you just drilled. It’s a tight fit. I sometimes use the anvil or flaring tool to help me get the eyelets in. It’s all still hand pressure, but the dies seems to help on occasion. You want the eyelets head flush with they kydex before you start to flare them.

Smaller eyelets or leather eyelets are easily set by hand with the appropriate flaring tool and a hammer. The flaring tool is a must for the kydex. Leather flaring tools do not work, even though the eyelets will. Flaring tools are available from TexasKnife.com.

Leather eyelets are different from the sheath eyelets TexasKnife sells. Leather eyelets are scored so they flare easily by hand. Kydex eyelets are smooth and create a nicer finish, but are tougher to set by hand. There is a special hand press available for setting eyelets and rivets. It’s a bit pricey.

TexasKnife offers hand tool directions which are to set the anvil die in a properly sized hole in a large piece of wood or block of metal. Set up the sheath with the eyelet in place. Orient the flaring die and strike with the hammer. That keeps things from bouncing all over from the impact. For the 1/4 inch eyelets, this doesn’t work quite as well.

I’ve faked a press using the 12 inch bar clamp. I set up the anvil and flaring die against the eyelet in the sheath. Holding the set up with one hand, I place the clamping faces at the base of the dies and begin clamping. Sometimes, one of the dies goes a bit crooked. The eyelet is still set however it’s a bit rough. A repeat of the flaring process usually smooths it out. The eyelet sets quickly and easily.

I sometimes strike set an eyelet with the dies that has a bit of a rough finish to smooth it up.

This method seems harder overall on the finish of the eyelets than the press.

Final shaping

With the sheath now set with eyelets, return to your original paper design and transfer the outline to the actual sheath as best you can by pencil. Freehand works just fine.

As I mentioned earlier, I cut off the excess material with a dremel. No matter what you use, you will probably need some relief cuts at various points in the final shaping to free up the blade as your turn corners and such. If you’re using a power tool for this, you need to keep the speed on the slower side as high speed cutting melts the kydex rather than cutting it. The melting is rather uncontrolled compared to the cutting and better for your cutting tools too.

The edge still needs some tweaking after this and sand paper is the way to go.

With all the cutting and sanding, it’s pretty common for some grit to get in the sheath. Blow it out with some canned air. Don’t wash it out as it’s hard to get all the water out.

Professional kydex has a shiny smooth edge. I haven’t seen this discussed anywhere, but I think there’s a heat finish on this edge besides the sanding. I noticed this effect in my heat gun experiments. I haven’t really figured out a way to do this well, but the heat gun is better than a lighter or other open flame.

At this point, I drill a drain hole. The tip of the knife outline in the kydex marks the point. Use a small bit, I like 5/64”. Use a light touch if you want the hole on one side only.

Over time, the sheath will wear and may loosen up. Using a heat gun or blow dryer you can focus heat on the spot that needs adjusting. I prefer the press to apply the pressure over other clamps or fingers as I’ve distorted sheaths this way with other means of pressure.

Other tweaks

You can custom mold pouches and clips to attach through the eyelets. Smaller objects without a narrow spot can be held in place with friction, though some scratching may occur.

Or you can build those in to the design with "wings" off the basic design outline. The wings will lie flat during the initial forming but can be heated separately with a heat gun for final molding without damaging the sheath's shape.

tags • kydex • tools • beginners • equiptment • diy • knife
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