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Tutorial: Leather-Covered Kydex Sheath for Big Knives

Discussion in 'Koster Knives' started by Daniel Koster, Jan 11, 2004.

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  1. Daniel Koster

    Daniel Koster www.kosterknives.com Knifemaker / Craftsman / Service Provider

    Oct 18, 2001
    Tutorial: Leather-Covered Kydex Sheath for a Big Knife

    A few months ago...:eek:...Shane Womer contacted me about making a leather-covered kydex sheath for a khukuri. We went through many iterations between then and now, and what you will see today is the result.

    Shane purchased a very stout 16.5" Chiruwa AK with a horn handle and brass fittings. It came with a nice karda/chakma set and standard black leather scabbard. What Shane wanted to do was be able to one-hand-draw the khukuri in a sheath that was also super-tough. Naturally, kydex and leather came immediately to mind. Kydex, because of its ability to be heatformed to shape. Leather, to add thickness, toughness and natural beauty. One other requirement was to make a "frog" to hold the sheath in an easy-to-draw position.

    While there are a few tutorials floating around about leather-covered kydex sheaths, they are mostly for small knives/neck-knives and there are none (to my knowledge) for big knives - such as Shane's enormous khukuri.

    Part of the reason this took so long - was having to set everything up. I would think that anyone with at least a beginner's skill level could create this same sheath in roughly 6-8 hours (not counting waiting time). Most of you will be able to do it quicker.

    I am not a professional sheath-maker and this is probably not the best way to accomplish this sheath. However, I have had the fortunate pleasure of consulting professionals on the path to getting this done and what I think I have is a good amateur sheath that can be put together by the most rudimentary Do-It-Yourself-er.

    Supplies List:

    3-4 Sq. Ft. of 8-10 oz. Veg. Tanned Leather = $13
    Foam pad (ie. sleeping pad, around 1/2"-1" thick) = $10
    2 Sq. Ft. of Kydex - mine was ~1/8" thick - you'll want at least 0.090" = $6
    4 Sq. Ft. of Plywood, scrap (or similar) = $5
    Contact Cement (not rubber cement, but contact cement) = $4
    Mink Oil = $4
    Beeswax = $4 (I used parafin wax)
    Waxed Thread - Brown = $3
    3M Blue Masking Tape = $2
    Sandpaper & sanding block - use ~180/200 grit = $2
    Saran Wrap = negligible
    Cardboard = negligible

    Tools needed:

    Hand Drill - variable speed is best (either cord or cordless)
    1/16" or 3/32" drill bit (I actually used a #50)
    Leather needles (1 curved, 2 straight)
    Knife (to cut leather, trim thread excess, etc.) - you pick
    Saw (for cutting the kydex)
    Double Boiler (or similar - see pic in tutorial)
    Kitchen Oven
    Pinch Clamps - at least 4
    Edge Groover (I think that's what it's called...)

    Optional Tools/Supplies:

    Edge Dressing
    Buffing wheel - for final finish
    Bandsaw - makes cutting the kydex faster (and messier :D)
    Belt sander - for cleaning up & rounding edges (also messier)

    I am not going to cover safety basics or shop basics, etc. Just use your head...ie, don't cut out the leather on your kitchen table...:rolleyes:
  2. Daniel Koster

    Daniel Koster www.kosterknives.com Knifemaker / Craftsman / Service Provider

    Oct 18, 2001

    First things first...an explanation on what we're doing here and why we're doing it.

    Personally, I don't really like the look of bare kydex on a big knife...even worse - kydex with rivets. So, I've searched out ways to get the form-fitting benefit of kydex as well as the beauty of more natural materials. I've used leather, fur and cloth over kydex. Each has its own merit and you benefit by having many options to choose from.

    So how do you put together a kydex sheath without rivets? That's where the leather (or fur, or cloth, etc.) comes in. In fact, on this particular sheath, the kydex takes a subservient role acting more as a liner, than a bonified sheath. There are many ways to skin this cat and I'm only going to go through one of them. Others are to drill holes in the kydex and sew up the edge side - like a pouch sheath. Another is to wrap thin leather around it and sew it up the back - much like standard scabbards and finnish belt knives. There are probably more ideas out there - maybe you'll come up with one even better.

    Now that we have our sheath process picked out (leather sheath with kydex liners) - we need to solve the problem of putting a curved knife into sheath. The khukuri makes this more of a challenge because often the blade is wider at the belly than at the bolster.

    First thing we do is get some cardboard to do some doodling.


    Lay the knife down and trace it's outline onto the cardboard.


    Next, to solve the problem of the wide belly, move the knife a few inches at a time and mark where the blade goes outside your initial tracing.






    Now you have a series of overlapping lines that show you how wide you need to make the mouth of the sheath.


    Draw a bold line outlining the overall shape:


    Then cut out that piece and tape it to your blade. Use 3M blue tape or drafting tape so that you don't leave a sticky, gooey mess on your blade. Set this aside, we'll come back to it later.
  3. Daniel Koster

    Daniel Koster www.kosterknives.com Knifemaker / Craftsman / Service Provider

    Oct 18, 2001
    Forming the Kydex:

    You'll need to make a padded form to press the kydex to shape. Again, there are many ways to tackle this problem, the way I chose was to buy a foam pad (used for camping) and glue several layers of it to some plywood. Since I'm using this only for big knives, I figured I'd make it rather large - around 12 x 24.



    I glued down 3 layers - with wood glue. Holds just fine.

    The handle of a khukuri is so much bigger around than the blade, that I modified one end of each pad to accept the bolster a little better and get a little better definition in the molded kydex around that area.


    Now, we're ready to go:

    blade & pads

    blade & kydex (cut to size)

    This is where the cardboard welt we made comes into play. Take your blade with the welt taped to it, give it a light coat of mineral oil and wrap it in several layers of saran wrap. This will allow the kydex to form to the desired shape without getting "too close". The oil will keep your blade from rusting during the process.


    While the lady of the house is away...;-)...toss the kydex on a cookie sheet and throw it in the oven for about 5-7 minutes (less for thinner kydex) at 350 degrees. You'll know it's ready because it will go completely limp.

  4. Daniel Koster

    Daniel Koster www.kosterknives.com Knifemaker / Craftsman / Service Provider

    Oct 18, 2001
    Now, while we're waiting...another explanation. There are a few different ways to make a kydex sheath. You can make it pouch style (folded over the spine) or pancake style (2 seperate pieces).

    Either way, the process is the same. Heat the kydex in your oven, put your knife and kydex inbetween the pads and stand on it until it cools down.

    (pouch style shown here)

    If you do it this way, you'll have to trim the excess above the spine and you'll end up with this:


    This was from one of the first leather/kydex sheaths I made:


    The pouch method is best if you want to replicate a khukuri scabbard with a wrapped and sewn thin leather cover. It is easier than the pancake method, and you can hide the opening in the kydex with leather.

    I didn't want a fold (in the kydex) over the spine on this one, so I chose to go with the pancake method. Basically, I cut out 2 pieces of kydex, and sandwiched everything together inbetween the pads.

    TIP: Sometimes thick kydex take a while to cool down - which means you might have to sit on it for an hour or so to ensure it doesn't move. To get around this, I use ice cubes to cool down "critical" areas once I have formed them, and then leave it in some clamps till it comes down to room temperature.

    (again, showing the pouch method)

    In the meantime...keep an eye out for shop-elves who will come and steal your kydex-forming pads and use them as a recliner...! :eek:


    By the way, this is where I get my kydex:


    Any 'ole plastics supplier should have it in stock. Or you can order it from most knifemaker supply shops.

    I should also add that it often takes me 2-3 times to get it right. If you screw it up, just toss the kydex back in the oven and it will unfold when it's heated back up.
  5. Daniel Koster

    Daniel Koster www.kosterknives.com Knifemaker / Craftsman / Service Provider

    Oct 18, 2001
    Making the adjustment welts

    Now that the kydex has had some time to cool, take it out of the clamps, lay the knife in the appropriately fitted spot, and trace the outline onto the kydex.


    Then, lay down your cardboard welt and trace around it as well.

    Lastly, add about 1/4" all the way around and mark that line.

    The reason you mark the lines is so that you can cut out the kydex one sheet at a time. If you've done your job right, the pieces will neatly match up after you cut them. Of course, there will always be need to do a little trimming and clean up.

    I cut it out at the bandsaw, clamp the pieces back together and "dry fit" it, that is, try to draw and sheath the knife with the clamps on it. If it's not perfect, don't worry - there's plenty of opportunity to correct it later.



    In this particular sheath, I have purposely left some gaps open. It was more important to Shane to have it easily drawn, than for it to lock up scary-tight. So, we'll make up some adjustment welts to fill the gaps. Plus, this will help hold the 2 pieces of kydex together while we cover it in leather.



    There is also a problem that the kydex doesn't touch at the bolster end - almost can't help it at this thickness of kydex. Really takes a lot of pressure to get it to conform.


    This is easily corrected by just heating that particular area with a blow-dryer for a minute or so and then bending it by hand.

    The kydex is now ready to be custom-fitted. This is where it gets tricky. You've got to be willing to play with it a bit. Adjusting a little here and there. Don't expect to get it right the first time. Take your time and you'll end up with a perfect fit.

    After horsing around with this one for a while, I figure out what I need to do to give it that "perfect fit". It needs a long welt along the blade side (a good idea anyway) to alleviate pressure from the belly trying to squeeze through where the cardboard welt was when heatformed, and it needs a small welt on the back because the spine on this one is actually thicker at the bend of the blade, than it is at the bolster.

    I cut some strips of thin leather (makes it easier if I want to use multiple layers in some places, single layers in other) and get ready for glue up. I've made marks to tell me how far to put the glue down.


    The welts get placed onto the kydex:


    And then the two pieces glued to each other. At this point, I put the knife back in just to make sure everything still fits ok.


    After everything is glued, I trim off the excess with a knife, round the edges at the belt sander and check the fit.

    Looks like it worked!

  6. Daniel Koster

    Daniel Koster www.kosterknives.com Knifemaker / Craftsman / Service Provider

    Oct 18, 2001
    Making the leather sheath

    The key to a succesful sheath is quality leather. Get good vegetable tanned tooling leather - usually comes in sides or splits. You can usually find it for $4-5 per Sq. Ft. and sometimes in splits as small as 14 Sq. Ft. Sometimes you have to buy the whole side. If you like leather, don't worry about it...you'll find a use for extra. :D


    You'll notice that I've taped together the kydex in certain spots. The tape is doing the job a clamp would do, but over a longer period of time. After fitting the leather to the kydex, the tape will come off and the "clamping action" will be replaced by stitching.

    Lay the knife down on the leather and trace around it. Again, after you have traced it, add 1/4" (min.) all the way around. If you've got extra, it doesn't hurt to use it since you can always take it off later (but you can't add it back!)


    On this sheath I decided to wetform before I stitch. Basically, I take the cut out pieces, wet (with warm water) only the necessary areas (the edges and the bolster area) and then press and squeeze it to shape. It feels kind of clumsy at first, but you'll quickly find a way to make it work for you.


    After a bunch of pinching, I get it to fit right and set it aside to dry out.

    When it's completely dry, it should be stiff and will hold its shape well. If you don't have it perfect, again, don't worry, you can come back and get it right later.

    Now, glue up the two pieces to the kydex. Use lots of contact cement and let it dry for at least 20 minutes and you'll get a solid glue-up. On this particular sheath, I decided to add yet another welt - this time out of the thick leather, to help protect the sheath when the belly of the blade is passed by the mouth of the sheath.


    The edges are pretty rough right now, so I'll take this to the belt sander with a high grit belt and smooth it out - including the mouth.

    When it's all finished, I do a quick fit test to see make sure everything is still ok...looks good so far!

  7. Daniel Koster

    Daniel Koster www.kosterknives.com Knifemaker / Craftsman / Service Provider

    Oct 18, 2001

    Set aside a good evening to finish the stitching. This takes a long time and make sure you don't feel pressured to rush it - you'll screw it up for sure.

    Again, the process I use is not the best out there, but for the do-it-yourself-er, it's likely to be one of the cheapest...;)

    Here's how it starts:


    What you are looking at is a stitch line. I used an edge groover to set the line. Then, I used a #5 layout wheel to mark the holes. After that, I get out my cordless drill with my #52 drill bit and drill the holes by hand. I do it at about chest height, looking down at the edge I'm drilling so that I can make sure it comes out the other side where I want it to.

    Here's where having a nice digicam helps.


    This is a super-zoomed closeup shot (the lens was about 1/4" away from it) of the stitch line after I have drilled the holes. Cool, eh? (the depth of field at this magnification is so thin, that most of the pic is out of focus, but that's ok with me - still a cool pic...I like how you can see the individual pores...)

    Ok, enough goofing off...

    Time to get back to work.

    Here's your basic stitching setup:


    The sheath is held in a vice, protected by a heavy towel - folded over many times.

    The next few pics will illustrate one method of stitching - again, there are many different kinds, but this one works good for me. You could also do a double-needle stitch. That would probably be quicker, actually.

    It takes time and experience to know how much thread to use....and I ought to know better...*groan*...I had too much thread and it took me forever to get this one done. So, don't ask me how much to use - I'll probably get it wrong.

    So here we go:

    Put the stitch through the first hole and pull the excess through it. That is, there should be equal amounts of thread on each side of the first stitch - left side is open, right side has the sewing awl.


    Push the awl into the second hole all the way, and then pull it back just a bit to make a loop.


    Take the free end of the thread and put it down through the loop and pull it through the full length.


    The pull the stitching awl back out of the hole.


    This completes the stitch. Pull on one side of the stitch until you notice that it "pops out" of the hole. Then pull the other way. See how much variation you can get? That's why it's important to try to keep the stitch in the center of the hole.

    When you've got it centered, start the next one by repeating the last 3 steps. Do this for a while and you can really get some speed built up. It saves wear and tear on the fingers too (vs. the double-needle method)

    (you can now see the welt I was referring to earlier)



    If you need to, at this point you can do more wetforming to get the look and fit you need.
  8. Daniel Koster

    Daniel Koster www.kosterknives.com Knifemaker / Craftsman / Service Provider

    Oct 18, 2001
    Catch & Frog

    No, we're not talking about playing Frogger...:D

    Rather, the frog and its catch allow a sheath or scabbard to hang independent of the belt loops. This is important with big, heavy knives and swords because you don't want a snug fit which would make sitting or walking very uncomfortable. So we ditch the standard belt loop for something a little more fancy.

    Also, a standard frog won't do, because if the knife in the case was hanging straight down, it would be a pain to draw one-handed. You can't get the proper grip on the handle. So, we're going to design a frog that is tilted at a slight angle to take advantage of the bend in the khukuri and allow for an easier draw.

    But first, we need to make the catch.

    That's simple enough - just 2 straps of leather that get glued near the top of the sheath. Cut 2 strips and lay them down as close to the bolster as you can. Then get the ends wet, and clamp it down. Once it is wetformed, remove the clamps, glue the pieces, put it together and put a few stitches in the ends. Here's a pic taken during the wetforming:


    Now we can better design the frog.

    First, I lay down the belt I have in mind (a wider 1-3/4" belt - at Shane's request) and trace it. Then I lay down the sheath with the knife in it and position it at the angle I want it to hang and trace around it. After some geometric doodling and fiddling (this was actually the hardest part of this whole process) I was able to simplify the frog down to this shape:


    What you are looking at is the frog being wetformed, but we'll get to that in a minute.

    Basically, it's just like a regular frog, but the end is turned at an angle. Once you have the shape you want, cut it out of a piece of folded paper, unfold it and cut it out of the leather. In order to make it hang right, you'll need to wet the belt loops (which is where the bend is)...make sense?

    Here's a pic from the side to help explain a little better.

    (by this point, I have already glued the piece and trimmed the edges)

    Now, I want to add a strap that goes around the frog to grab the "catch" when the sheath slides in.

    Just lay the sheath over the frog, position it where you want it and make sure you cut a strap that's long enough to go all the way around. (This will make more sense once you see the finished sheath)

    Here's the front side, showing the strap:


    And the back, showing stitching:

    (the stitching on this is a little tricky and requires a curved leather needle)

    The last step is to add a little keeper to the frog. This is to help keep the sheath in place while the knife is being drawn. I forgot to take a pic before I did the finishing, so here it is in its oily glory:


    And a more detailed pic showing how it all works:
    (again, after finishing)

  9. Daniel Koster

    Daniel Koster www.kosterknives.com Knifemaker / Craftsman / Service Provider

    Oct 18, 2001

    The easiest method I have found so far is to Oil and Wax the leather. I know it is not the best way, and until somebody comes and relieves me of my stash of wax and oil and shows me a better way, I'm stuck with it.

    Ok, with that out of the way....

    Usually, while I'm working on something else, I will set some wax to melting. Since it is flammable, I use a double boiler method.

    Water in the bottom pan, wax and oil in the top pan.


    Since I store my wax in a quart jar, this is usually how I have to get it started. Otherwise, if I put the jar in the top pan, it takes forever.


    So, I heat the wax/oil combination until it's all melted. Be sure to keep track of the water level in the bottom pan and make sure the lady of the house is away (or asleep, in this case...:eek: )

    Once the wax is hot, just hold the sheath over the top pan (this is why I use a very large metal mixing bowl) and with a large metal spoon/ladle, drizzle the mixture down the side of the sheath. This needs to be done as quickly as possible to reduce excessive wax build-up. When the sheath is completely covered, lay it down over some paper towels and with a soft cloth, rub the excess wax away from both sides. Don't forget to get all the edges covered properly. It can be a little frustrating if you get extra wax buildup, but don't worry because that can be corrected later. For now, do as much cleanup as you can and make sure everything has been treated.

    Now, stick it in the freezer for a minute or two for it to cool down and harden a bit more.

    Repeat the same process with the Frog.

    If you've done it right, you'll get a nice rich dark brown color and a sheath that is water resistant. The leather is also smooth, yet stiff. A good combination for heavy duty use.

    At this point, the leather in the sheath is still "processing" so I go ahead and test fit it with the knife a few times to make sure I have the fit I want. Usually, the leather will tighten up a bit, so I try to leave extra room at the beginning. This time, it tightened up quite a bit, so I alleviate that by heating up the sheath gently and then inserting the knife (which has been oiled and covered with lots of saran wrap and tape) and let it sit inside the sheath for a day or two. This will help it expand a little more. Normally, I'd want it tight, but this time, I needed it to be an easy one-hand-draw, so I had to make some room.

    Now, if you've had any problems with your wax not setting right, or building up too much, there's an easy solution - again the blow-dryer. Just point it at the trouble spot and it magically evens out the finish across the area. I'm not making this up. It is a wonderful thing to see when your screwed up finish suddenly looks as good as everything else around it. The reason this works is that the finish probably didn't penetrate the leather as well in that particular spot, and so when it is spot-heated it forces it to let the wax/oil penetrate. Works every time. Just be careful not to hold it there too long, because your finish will puddle up and run off - which can be bad...:D

    Now for some pics of the finished product!


    (same side, different camera angle)

    (on the belt)

    It draws nicely and stays put on the belt. It's an easy one-hand-draw and doesn't bang against my leg when I want. (You khukuri owners out there will especially like this;))

    Well that's it!

    All in all, this took me about 2-3 months. Something tells me it will take you less!
  10. etp777


    Aug 12, 2002
    GOtta love those spring clamps. I gotta buy another package of 5 next time I bring in some cash, let me do several knives/whatever at once

    Definitely a good tutorial. On the long list of thigns I have to try sometime. Right behind leather and kydex sheathes for normal size knives. :)
  11. Roadrunner


    Jun 9, 1999
    Sure beats my 100 mile-an-hour tape job! In all seriousness, thanks for posting this one Dan, that's a really great tutorial. I can't wait to try it out on my WWII, it looks like an excellent rig.
  12. hollowdweller


    Sep 22, 2003
    That is totally cool and understandable, and totally nice of you to post it to help other folks:) I never realized you could get kydex that thick
  13. WarrenR


    Dec 27, 2003
    Great tutorial Dan!
    That sheath definitely states "contents: serious
    business". :D :D
  14. hoghead


    Dec 17, 2001
    I'd been kinda wonderin'.
    You do great work Dan. I'm impressed with that sheath. :) :) Shane ought to really like that khuk.:D
  15. rjudoka


    Oct 11, 2003
    Nice tutorial, Dan. Thanks for posting it. This has been on my to do list for awhile and your info will really help.

  16. DannyinJapan


    Oct 9, 2003
    You know, that was really good. I learned alot just now.
    I wonder if Terry Sisco can do that kind of work too.
    Really nice Dan, thanks.

    (i think in sword terms, they call that a hanger as opposed to a frog)
  17. Ferrous Wheel

    Ferrous Wheel

    May 16, 2002
    a beauty, Pen. I do some stuff diff, but I'm gonna hafta use a few things you did! That stitcher tool is cool. That would save me a buncha time and fingerwear.

    I prefer thinner kydex as well, and heat my ove to the loest setting. Gotta love that wonderful soapy-chem smell of the kydex in the oven, eh?

    Great description of the Cuir bolli process (waxed leather) as well. Wonderful tutorial!

  18. Nasty

    Nasty Chief Cook & Bottle Wash

    Nov 11, 2003
    Nice work on both the rig and the tutoral Dan!

    Now then, I'd like mine in a crossdraw and black...and could you please convex the edge for me while you're at it?

    :D ;) :D ;) :D
  19. ddean


    Mar 26, 2002
    Now that is a tutorial.
  20. clearblue


    Oct 22, 2002
    AWESOME!! Dan,

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