Lining Kydex Sheaths

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phatjohn

Well-Known Member
Ok gents here's the scenario. I'm a new knife maker. I've got a good friend that is letting me put my knives in his gun store. I stopped in the other day and my friend told me that their was another local maker in the shop ragging on one of my knives because the blade is showing signs of wear from the kydex sheath I made for it (the knife has a bead blasted finish). This guy said I should be able to line it with something. There are a couple of problems I see with lining a kydex sheath with leather or neoprene, ect.....

1) Moisture- Kydex doesn't breath, if I put a liner in a kydex sheath and it gets wet where is the moisture gonna go? You put a carbon steel knife in a wet sock we all know whats gonna happen.

2) Durability- The particular knife he was ragging on is a Bowie inspired fighter. The point on it is very sharp. In an unlined Kydex sheath, you put the blade in crooked and the inside of the sheath is gonna get scratched, no big deal. With a lined sheath, what happens if you put the blade in crooked and the tip catches and tears the lining material? That just seems like a huge headache waiting to happen.

So my question is this. Has anyone who works with kydex regularly ever lined a knife sheath? If so, what did you use and how did you do it? Have you had any problems with the things I listed above?

As an aside, I got pretty ticked off at the guy criticizing my work. We don't know each other and based on his comments, I don't think he's ever worked with kydex before and doesn't understand the material.

P.S. Here is a picture of the knife in question.

DSC00645.jpg
 
I work with kydex a lot and it scratches my knives as well. Some things I've noticed - the scratching is of course lengthwise, so a hand applied lengthwise finish almost totally masks it. My combat knives with the machine finish going perpendicular to the blade showed the scratching immediately and it was a real eyesore. Same deal with a blasted finish. Also, I can keep the kydex absolutely clean, wipe the sheath out as mine are held with binding posts, and it will still scratch - evidently there is something in the kydex itself that is able to abrade the steel. If you get a chunk of ceramic abrasive in there it's readily evident but the finer "wear" scratching is nothing I've been able to resolve. Also, the kydex evidently has a negative charge to it as it really sucks up the dust which doesn't help things. I've delivered knives and had the client sand the throat on several occasions to clean up a perceived burr and fill the sheath with the sandpaper grit, had them used on a beach fishing and got sand grains inside, you name it. After those deals, even if I scrape the inside of the sheath and wipe it down heavily with a solvent, it is pretty much shot for protecting the finish.

Now, I'm a huge fan of the kydex and I build them for the bull. There are a lot of reasons I go with it and will continue to do so. One thing I've noticed - if I rough up the inside of the area where my welt fits with a 60 grit belt and give it some "tooth" I can apply Barge cement to it and stick the whole assembly together for drilling my post and attachment holes. Works great and it sticks good enough you have to clean the whole works with acetone if you don't stick them together lined up the first time. It's not enough to make a structural joint but it works - I've thought of lining them with 3 ounce with barge between just like a leather lamination. My issue with doing so is that the liner has to come to the edge of the sheath so it's held by the posts too, and it's going to want to squish at different rates depending on where it is in the stack and might make the sheath wavy. What you've mentioned is another worry - that thin leather sooner or later is going to come apart in there, plus want to hold water.

Because of these things I've just stayed the course and been very explicit that the sheath will cause some scratching on the knife no matter what you do, that it's the nature of the beast and the benefits of the kydex outweigh any downsides.
 
I used to think that it was something inherent to kydex that caused scratching on the blades... I even cut a couple of pieces of scrap kydex and purposefully rubbed a knife blade with them. I THOUGHT I was seeing scratches, but a lot of times it's just a "smudge" that will wipe off with a bit of buffing or acetone.

Now what about the deep scratches? It's just like Frank said. This normally happenes AFTER the knife and sheath are made, or even AS you are finishing the sheath. I use the same bandsaw that I cut my blades with to rough cut my sheaths. Sometimes a piece of grit or metal shavings will come off the blade and imbed into my kydex. Some times it's from the sanding media on the belts that I use to shape the finished sheath. Some times it might come off of my buffer as I'm burnishing the edges.

I've also noticed that my knives sometimes are magetized enough to pick up some stray grit or metal dust in between sheathing and unsheathing a couple of times. I think there's even something to the static charge theory of attracting dust, or even magnetizing the blade to an extent.

How can we avoid this? Well, for one, I do try to demagnetize my blades before sheathing them. I also try to clean everything thoroughly as I'm making a sheath, and then I try to blow any dust and grit out. I'll often shine a light into the sheath to see if I pick up any grit reflections.

Ideally, I should probably have a dedicated bandsaw blade specifically for kydex, as well as dedicated belts that I've already cleaned or broken in. Some anti-static spray probably wouldn't hurt for the kydex.

Sometimes, I will also tape my knives eith a layer of duct tape or a couple layers of masking tape so that there's a little bit of clearance after I press my sheath.

All that said, I don't think there's a way to ultimately avoid ALL kydex related scratching, as unless you work in a lab grade environment, you're bound to get some kind of dust or grit in your sheath. But then again, knives that get used are going to scratch up anyhow.
 
I made a kydex sheath for my personal knife. The knife is small enough to carry in my pocket and it's nice to take out and show people a real example when discussing my hobby. The kydex was nice and durable, and did great in my pocket, but it scratched the 400-grit finish on my blade. It also scuffed the stabilized wood bolsters a bit. I tried re-heating and re-fitting, but that didn't change anything. I too thought about adding a liner, but couldn't come up with anything I thought would work. So recently I made a compact leather sheath to replace it. I was worried about durability in my pocket, but so far it works great. I'm not sure if I will give kydex another shot on a future knife.
 
Getting a scratched blade from Kydex is just nature of the beast if you will. I'll go through the process I use when making a sheath.

1. Double to triple layer the masking tape on your blade before pressing your sheath. I only use one layer on the handle for wooden handles and leave the handle unprotected for phenolics. This allows a little more room for your blade in the sheath and a very tight lock up on your handle thus preventing as much rubbing of the blade inside of the sheath (similar to the saya of a katana only having contact with the habaki).

2. Ensure that your sheath is a perfect fit. Often times there will be shifting between pressing and shaping. Prior to removing the knife from the formed Kydex, I secure everything in place with masking tape. I leave the knife inside the formed Kydex until after I drill my construction holes.

3. As I drill my construction holes, I place my eyelets or binding posts (without flaring the eyelets of course). Once again, this prevents shifting. I then leave the eyelets or binder posts in place throughout my shaping process. I have a dozen or so eyelets that I use for "mock up" as they will get scratched and damaged during shaping.

4. Once everything is shaped to my liking, I take apart the sheath and thoroughly clean it. I prefer a two piece sheath for this very reason. I want the sheath perfectly clean on the inside before I permanently flare the eyelets Nd find that dificult to do using the fold over method. I clean using Goo B Gone and then dish soap and water.

5. Inspect the sheath thoroughly for burrs, hand sand flaws, and re-clean as needed.

6. I then remove all tape from the knife and clean it prior to re-tapeing it with a single layer of masking tape. Applying a fresh layer of tape prevents contaminating the interior of the sheath.

7. Lastly, I flare my eyelets if that is the method the customer has requested. I attempt to encourage my sheath customers to pay the extra few dollars for binder posts and machine screws as it allows you to take the sheath apart for cleaning.

Also, I always drill a "drain hole" at the tip of the blade for flushing the sheath and allowing the sheath to drain water properly.
 
As said Kydex doesn't scratch but holds grit that does

Definaly can be reduced with taping up a good space on the blade which also helps stop moisture build up

I spray the inside with Dry lube silicone spray this dries to a coating and helps stop Grit and moisture sticking

and bead blasted is a horrible finish for a knife and seems to show up any mark from anything

ATB

Duncan
 
Thank you to the OP (John?) for starting this thread - and to the folks who gave such good detailed replies. There is some VERY good info here. I've only made a couple of Kydex sheaths, and can tell exactly what ya'll are talking about.

Ken H>
 
i had the same question, thanks for asking again u seem to be getting more respones then i did. great knife by the way.
 
oh Kydex is great and easy and tough stuff i like using it not a problem that it scratches. but other than leather what else can be used for a shealth?? that will hold the knife in place but not causes scratching??? i got a tratical knife i want a sheath for but i need it to be queit when pulling the knife and keep it in place as u move around but also id like for it not to be all scratched up. can i have my cake and eat it too?? or am i living in a fantasy world of knife making?? plz i need someone to guide me though this land of sheaths and teach me the ways of the masters lol:detective:
 
I'm still thinking and working on this one. I'm going to a lengthwise hand-rubbed finish for any Kydex sheathed knives in the mean time - I rather enjoy being able to show off my "across the blade" machine applied finish and this is more a stop gap to avoid the very noticeable across the grain scuffing. Attempts at segregating the Kydex work from the rest of the shop and laboratory level cleanliness are helping somewhat. One other issue is that any lining adds weight to the sheath as well as thickness, plus the aforementioned snagging issue. I've go one with the old style coming up in a few minutes to show off and I'll say that the stainless CPM grades are a little less likely to scuff up than regular carbon steel for some reason.
 
There is a reason leather is still around for sheaths. It doesn't scratch up knives like Kydex does.
It is simply part of the territory, kydex will leave some marks on a blade. It can be minimized with some of the steps the guys have mentioned already but it won't ever go away. Most guys that have knives in kydex get this and accept it. Other enthusiasts that have less experience with kydex are bothered to see these sheath marks. I think everyone has tried to line a kydex sheath to minimize the marks but you rarely actually see it on a knife for sale.

This will be hard to accept and I understand not accepting it:
Don't get mad at the guy. Getting harsh criticism on any knife or sheath you make is possibly the single best motivator for upping your game than anything else you will do in knife making. Those tough comments really sting. I always remember a knife I sold that came back to me due to little flaws in the finish. I vowed then to never have another one sent back after that. It was one best things that ever happened in my early knife making career.
 
Thanks for the words of wisdom Boss, you're right I have tried to up my game. I've been playing with my finishes lately so this isn't a dead subject for me. So far, I keep everything as clean as possible. I use kydex rivets with masking tape over them to hold everything so it's lined up correctly while I'm finishing and tweaking the kydex. I've also found that binder clips (the things you hold a stack of papers together with) work really well for holding the halves of kydex together when you don't have a third hand handy. So far, a brushed finish knife seems to hide the scratches the best but there are times when I can't resist that bead blasted look. I think I may have found a solution to that problem but I'm still tinkering and testing it so I'll reserve judgment on that for now.
 
I am late to the party but I have linned kydex sheaths before and its very easy to do. When I was making CCW holsters I hated how the kydex wore on the finish of my handguns so i started linning them with either deer skin or 3-4 oz leather. If you have a good press and properly heat your kydex to 400* it will form just fine with great detail even with the leather around the knife. Goop will hold the leather just fine.

Going with a brushed finish running parallel to the edge as mentioned will mask a lot of scratches if you dont polish the blade too high.

I am not sure why some scoff at a linned kydex sheath since if it were full leather it would still serve the same purpose, however I find it more enjoyable to form the kydex than I do leather.

I really like the look and use of hybrids with removable liners but that puts us back at the same point with scratches.

On some holsters there was a small spot of leather just at the contact points. This may be a good compromise but I have not tried it in a sheath.
 
FWIW, I found "peal n stick" black felt at Michaels Craft Store. Felt is formable. For that matter you can use spray on adhesive and use regular felt.
 
One of the last kydex sheaths I made used 1/4" chicago screws instead of eyelets to secure the two halves. The sheath was lined and should it need to be cleaned or dried its a simple matter of taking the screws out and separating the halves. Best of both worlds and effective. I dont line every kydex sheath I make but its an option and sensible.
 
I've recently started experimenting with various lining materials. Velvet, leather, denim, etc. Most work well, some better than others....

Then, although it takes a bit of blade prep, with double sided tape and strips of material trimmed just right to allow the kydex to settle along the spine n the very edge of the cutting edge. Newest variant I'm attempting is trying to get it to where just the tip is saddled n the handle/guard/handle design dictates. Gone through a bit of PVC scraps as guinea pigs, as not to waste my kydex.

Also found when leaving the void, to leave a tad bit bigger drain hole to allow debris to pass thru easier(just in case), so as to not risk having a nugget get drug across the blade when sheathing. Again, all experimentation.... Even starting fiddling around with my pack ax.
 
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