Does kydex scratch knives?

joeyza

joeyza

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Feb 27, 2013
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was just wondering this cause I've heard this a few times on youtube and some other reviews. Does anyone have any personal experience with this? My specific case is a 154cm blade which I have never used having scratches appear on it and the only thing i can think of is the kydex sheath.
I always thought a less hard material cannot scratch a harder material so if it is the kydex I dont understand how this would happen??
 
The material itself wouldn't; it's too soft. BUT, if some dust or other grit were stuck to or embedded in the Kydex, that can scratch a blade easily. This is generally true of any sheath that's rigid enough to exert some pressure against the blade. If it's dirty, it can scratch it (and it usually will). Even one grain or speck of dust or other grit on the blade, when inserted into the sheath, will be enough.


David
 
Kydex cannot scratch knives. However if there is debris inside the kydex sheath, some of it may be hard enough to scratch the blade.
 
My personal experience is that once it becomes scratched or worn (no longer factory smooth) it can scratch hardened steel. Have seen it scratch many a handgun and knife blade, finally did a test of my own. One clean knife, one piece of Kydex out of the box and wiped with cotton cloth. Take knife blade pressed flat on Kydex and rub back and forth. Have done this test a couple of times because it doesn't make sense based on the ingredients, but it never fails to make small scratches on the blade once the Kydex gets scuffed up. If you can manage to keep it glossy smooth it seems to do much better - I've taken to lining all my Kydex sheaths with boiled leather.
 
HH, I'd bet the scuffing/scratching in the Kydex is trapping or holding some dust or other grit, which is scratching the blade. I suppose it's possible that a dirty manufacturing process (not of the raw Kydex, but making/forming the sheath itself) might leave some dust or whatever embedded in the material. Maybe grit left from factory cutting/sanding operations(?). As you mentioned, keeping it glossy smooth should help in minimizing the places for additional dust or grit to embed in it.


David
 
I'm interested to see what other folks experiences are re this. As mentioned - I wash the knife down good, use a sheet of Kydex that was never formed, still flat, right from the box, wiped it clean, and it never fails. Have done this test three times with different knives. Also, I have never owned a Kydex sheath or holster that didn't scratch whatever it was holding, in most cases pretty quickly, even from reputable mfgs. Not just carbon steel, but stainless too. Once I started lining everything with leather that issue disappeared, even though these are now some rather tight-fitting sheaths. I'll get some leather polish action, but no scratching.

I know the steels harder than Kydex, but I have to go with my experience on this one. If you don't want the knife to get scratched one should be very particular about how they remove/return their knife, and what kind of clearance the knife has inside the sheath.
 
In searching on how Kydex and/or sheaths made from it are made, I found this interesting post on another forum, from someone experienced (take it for whatever it may be worth?) in making sheaths from it. It does sound like keeping dust/sanding grit off the stuff is critical and challenging. There's also mention of adhesives (from tape) used in the molding process, which has potential to trap & hold grit, if it's not completely cleaned up:

( from site -->: http://www.knifeforums.com/forums/showtopic.php?tid/918486/ ):
"Kydex CANNOT Scratch a knife PERIOD. Kydex is softer than steel. Kydex sheaths will make a mark on a polished steel blade but it is NOT a scratch.

(...)

As for grit in the sheath, the biggest part of the problem comes from cleaning as you know, but you cannot forget tape residue left inside the sheath from the molding process. Heat breaks down the adhesive and it oozes out onto the inside for the sheath.

Sanding grit is a big issue when you make kydex sheaths; the rule in my shop is to blow out the sheath EVERY TIME a knife is test fitted. We also wipe out the inside of the sheath before riveting with alcohol to remove any tape residue that will grab any grit falling inside the sheath.

We also clean the knife, put it far away from the grinding and cleaning area and religiously wipe it down before every test fitting, again to keep grit out of the sheath. When I started actually cleaning the knife as well as the sheath much of the problem disappeared.

I also leave a lot of room inside the sheath for the knife, using as many as four layers of tape in areas that will be small when the sheath is complete. This leaves room for the crap that falls inside to be away from the blade in use. A single layer at the point and the sheath will still seem to lockup "snug."

One last consideration, Kydex sheaths are ideal for USING KNIVES. Knives in use will show wear so the rub marks left by kydex aren't a realistic concern. If the knife is for show, it either stays out of the sheath or should be sheathed in leather, although even leather will "mark" a polished blade.

The proper measure for a kydex sheath is simple, locks up tight enough to hold the knife in its intended environment and releases the knife smoothly and easily. Beyond that you're looking for headaches."
Click to expand...

Being a (relatively) soft & plastic material, it doesn't seem too illogical to assume some grit particles could become easily embedded in the stuff, especially if those particles get 'squeezed' between blade and sheath, when inserting or removing it (sort of like rubbing/embedding grit into a wooden strop). May be next to impossible to clean it off (without re-sanding), if the particles get embedded.

Edit:
Here's some more of the same type of commentary (particles in sheaths making scratches), from a thread in the Makers' sub-forum here -->: http://www.bladeforums.com/forums/showthread.php/334451-Avoiding-kydex-scratches


David
 
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I agree it seems impossible.
Based on my simple test, which can be repeated by anyone with a clean piece of Kydex and a clean knife, I don't think the answer is all that straightforward. I didn't conduct it over a period of time or anything, it didn't have a chance to get a handful of grit embedded unless it removed it from the blade face after being cleaned. Maybe others have different outcome and in that case I shrug and admit I don't have a clue. I came away thinking that the Kydex, if allowed to become rough, will scratch steel. Either that, or the Kydex is capable of pulling pieces of steel from a smooth knife face and then scratching same with these pieces. How is it pulling the steel off in the first place? Admittedly, I did this test three times, not hundreds. It did jibe with my personal experiences - I have never owned a Kydex sheath or holster that didn't scrape its contents. Some were better constructed to minimize contact, but there isn't (wasn't, as I lined them all, even the holsters) a single one that didn't scrape. The marks are indeed scratches and not surface marring. As I said, I'm very interested to hear what other folks have found.
 
I met Ed Caffery at a blade show years ago. I asked him about working with kydex. One of the things he told me is to wrap the blade in masking tape. This gives the blade a little bit of clearance in the sheath. So with the extra clearance and thoroughly cleaning the inside of the sheath with a rag and Armor All seems to keep my knives from getting scratched.

Ric
 
OK this is getting to me... the bit about Kydex not scratching metal, but polishing it... the act of polishing in itself is scratching the surface of what you are polishing... think about it... you're REMOVING the high spots... this is the whole reason why you go to a higher grit when you start your polishing process... and you don't end by rubbing it on a sheet of plastic...

Will it scratch your blade, yes it will, if there is a bit of debris in there from the sanding or trimming process, there can be enough pressure between the sheath and the blade to mar it.... I would probably won't be a deep gouge, and most likely rub out easy enough.

If your sheath is properly made and care is taken in post forming/cutting/sanding process, you shouldn't have to worry, just keep your sheath clean.

I've made the majority of my Kydex/Boltaron sheaths keeping that in mind and I don't have a scratch or mar on any of my knives...

EDIT: This was not meant to offend or start an argument... this is highly subjective on what a "scratch" is
/rant

EDIT2: In regards to the hard soft bit, ice cuts granite (take a look at El Cap and Half Dome in Yosemite) it just takes time (and this is an extreme example I know)

I should also add that I am assuming that the debris in the sheath is from the sheath itself, and that the sheath itself if properly made and prepared should do no damage.
 
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Recently, I bought a kydex sheath on eBay for my brand new pristine Fallkniven A1 with a satin finish. Being new to knife collecting, I too assumed that kydex would not leave significant scratches, especially on VG 10. I was mistaken. It left deep enough scratches that catches on my fingernail over two cm in length right on the VG-10, beneath the laminate line. Truth be told, it pained me to see it marred. I am trying to at least recoup my losses on the crappy sheath, for which I am having to fight the seller who denies any responsibility.

I don't know if it would be possible for me to remove such deep scratches by hand. I don't have the expertise to try to machine them off. I would very much appreciate any suggestions. Thanks in advance.
 
Kydex scratched the crap out of my Carter neck knife (with ~ 61-62 rockwell)!!!

I washed and washed and washed and washed and washed some more.
It doesn't scratch anymore.

Pretty confident that it small metal shavings or sand that's scratching the surface.
I always clean my blade if I can before I put them back into the sheath now.
 
nuskinner

nuskinner


Not sure if this posting will work. The scratches were as described (the most pronounced one was about two cm long, deep enough to catch a nail, on the VG 10 below the laminate line).
 
Unfortunately, that looks like it'll be impossible to get out properly.
I was hoping that the blade surface would be somewhat mirror polish.
Then you can buy a 40 dollar buffer from a hardware store and buff it out.
You won't get rid of the scratches if they are deep enough to catch your finger nails, but once you buff them you won't even notice them unless you inspect them carefully.

But your knife has grained satin look from the belt grinder they used (maybe even a touch of sand blasting). So if you buff, you'll lose that satin look, which isn't something that I can recommend. You'd need to completely re-sand the whole blade to give it the nice uniform look, and that's a major operation to do it well.

You could send it back to Fallkniven and have them refurnish the surface, but if it were me I'd just turn that baby into a survival beater knife. Good luck.
 
Obsessed with Edges said:
One last consideration, Kydex sheaths are ideal for USING KNIVES. Knives in use will show wear so the rub marks left by kydex aren't a realistic concern. If the knife is for show, it either stays out of the sheath or should be sheathed in leather, although even leather will "mark" a polished blade.


David
Click to expand...

This part really stood out for me. Even leather lined with the hide of a velveteen rabiit could still get sand/grit in it and scuff or scratch the knife... To me it's a non issue as all my knives are users. A well made kydex sheath shouldn't really touch the blade at all; only contact at the handle/guard area. At least that's what I've seen from the likes of David Brown and Al Welke... :D YMMV.
 
Czechmate said:
This part really stood out for me. Even leather lined with the hide of a velveteen rabiit could still get sand/grit in it and scuff or scratch the knife... To me it's a non issue as all my knives are users. A well made kydex sheath shouldn't really touch the blade at all; only contact at the handle/guard area. At least that's what I've seen from the likes of David Brown and Al Welke... :D YMMV.
Click to expand...

That quoted text isn't my wording (as your quote box might seem to allude), but instead quoted from another person's comments in the linked thread in my earlier post. Just want to clarify that. Though I generally agree with what he said... ;)


David
 
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