Kydex Scratches

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blish

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Mar 11, 2006
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I have two very nicely made knives (Ed Chavar) that have both been scratched by their kydex sheaths. Neither knife was carried so I did not get sand into the sheath.

Like to know the why of this and some thoughts for fixing the problem.
 
blish said:
I have two very nicely made knives (Ed Chavar) that have both been scratched by their kydex sheaths. Neither knife was carried so I did not get sand into the sheath.

Like to know the why of this and some thoughts for fixing the problem.
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There was undoubtly dirt on the kydex when the maker made the sheath.

Two possibilites, 1, Knife shops always have stray grit from belts and grinders all over the place. A dust removal can't get it all. plus you make the sheath with tools like saws and belt grinders, Grit from those tools will end up in the sheath. 2, Kydex being plastic does an excelent job of picking up and storing static electricity. Dust and grit stick to the kydex because of the static charge. When I make kydex sheaths I always scrub the smooth side throughly with dish soap and a kitchen scotchbrite sponge before I mold it to the blade. I'd wager there are probably a lot of makers who look at the kydex and if it looks clean "It is clean" I usually make 2 piece sheathes so they can be cleaned before final assembly.
 
I think that part of this has to do with how the sheath is made. I have made a lot of sheaths and as long as the user keeps them free of dirt scratches to the blade are kept to a minimum. I cover the knifes blade in blue painters tape. That give a little bit of clearance for the blade to slide in and out of the sheath, but allows for enough tension to retain the knife in the sheath until needed. IMHO I think this helps cut down on scratches that are noticed on the blade. There again the user needs to keep the inside of the sheath free of dirt and debris. I also add a 1/16" hole near the tip of the blade to allow water to drain from the sheath. I hope this helps.
 
Axeldoomeyer is correct. It has everything to do with how the sheath is made. By taping the blade (the blue painter's tape is great stuff), you can build some "freeplay" around the knife, thereby preventing the inside of the sheath from rubbing on the blade. It's a balancing act between just enough and too much. Too much and the knife will move around, rattle, and rub. Drawstroke has some to do with it also - if you twist the knife before it's completely out of the sheath, you'll get rub marks.
 
Thanks for the info guys- I just bought my girlfriend a Shun Classic paring knife to use at work (what is the point of being a knifers girlfriend if you are carrying a 2 cent cheap POS) and it needed a sheath. After using it for a couple of days the blade was getting scratched up. I cleaned the kydex before final folding but I think I understand why the scratches appeared now- time to get painters tape!
 
I like kydex sheaths, but EVERY kydex sheath I have ever seen has scratched the knife. And, I believe I've seen kydex sheaths made by just about everyone you can think of. Just the nature of the game, and I accept it for what it is.
 
They all scratch, all the time. The reason is dirt in the sheath, not the material itself, but that said, it is impossible to make a synthetic sheath that doesn't get crud in it eventually. That's just the downside you have to consider with them all. You can tape the blade with a few layers of tape, but leave an inch at the point untaped, and it will hold the last inch, but not the part you taped, but eventually it's all going to get scratched up. I can't tell you how many pretty knives I've made and shipped out with scratches from fitting the sheath, but I always warn people ahead of time that that is what is going to happen, so they aren't surprised. Damn Kydex!
 
Dang. I've been poking around the forums for stuff about Kydex causing scratches, and had hoped there was a solution which would still allow a snug fit. Seems not. I just got done polishing a long dagger to a really nice shine... put it into the sheath... .093" Kydex fitted nicely to the blade then covered in thin leather sewn and glued in place. Look of leather, security of Kydex. Anyway, put it into the sheath and pulled it out a couple of times, testing the final fit, and there was a nice long scratch about halfway down the blade. I'd even gone so far as to swab out the sheath first with a bit of new chamoix on a copper wire. Guess I'll not bother with form fitting any more. A couple of layers of painter's tape when fitting and some sort of retention at the guard will work fine. Just doesn't have the same feel as a nice fit, snicking out of the sheath.
 
The scratches are definately from sandpaper grit left behind or dirt that just gets in them. Once I shape and sand my sheaths I wash them twice in soap and water to get all the sanding grit out. I also put two layers of painters tape on a blade being pressed. Knife is still extremely secure but adds that very small amount of space to help with dirt or whatever rubbing the bladeinside the sheath. Like stated above the end result is always scratches with this kind of sheath. There is no give like leather.
 
I have found that using 2 layers of "el cheapo" masking tape from the hardware store on the blade prior to molding and then heating the kydex then molding to shape and allowing the kydex to cool to room temperature and then shaping the sheath to final desired shape and yadda yadda and then running water through the sheath as violently as possible to get out all the grit and then padding dry with a dish towel and then setting your rivets in a different place (than where you do your grinding) and inserting the blade back into the sheath or adjusting retention elsewhere of your shop will almost 100% of the time prevent any scratching at all on the blade.

Apparently i do not believe in punctuation and run on sentences ! :)

DO NOT BUFF the edges of the sheath with any kind of grease compound (Even if it makes it look pretty) or any compound of any kind. Use a scotch brite pad to smooth out the edges of the sheath. Stay clear of dust and particles after (should you rivet the sheath together) or you can do it the way Chiro75 does and do not put rivets so you can ocassionally clean out the sheath of debris and whatever.
 
There's a 'serious fighter' thread around here lately where one guy shows blurry pictures of a breakaway Kydex sheath. Kind of a neat idea, though I suppose it'd only work with the thicker Kydex as stiffness would be needed. No rivets at all down one side. You could make a folded Kydex sheath with webbing/cord slots/holes carved into the folded side of the blade. The other side is left open, but moulded tightly around the blade, so that the blade may be drawn as normally from the top (or bottom if inverted carry as he showed), or may be "punched' out the side slot. Seems to add the benefit of being able to more thoroughly clean the inside on a regular basis. Easy enough to make a thinner shaft, aluminum maybe, wrap that in clean cloth, insert from the end and then push it out the side. A few cycles like that should wipe any grit out of the innards.
 
Tom Maringer may be who you are talking about as he makes that style of sheath. And his knives are definitely serious.
 
Oh I know! I was just commenting on the photos, which didn't really measure up to the pictures of his blades and handles. The lighting and focus on the sheath in the shot where he (or someone else?) was wearing the thing didn't really show how the side of the sheath opens. Not too hard to guess, but he also mentioned a thumb release of some sort for top-drawing... I just wished there were more details. But then again, a maker can't give away all his secrets! The handles I saw from that maker looked absolutely gorgeous.
 
One way to hide inevitable kydex-related scuffing is to 'hand-rub' the blade lengthwise when finishing (so the sating-finish 'scratches' run point-to-pommel, not perpendicular to the edge like you get when you first grind a blade.)
A lot of makers do customs like this.
This works great and makes these scuffs less noticeable ... but ... if you actually use the knife, you'll tend to get scuffs which run perpendicular to the cutting edge.
Take your pick ... scuffs from Kydex or scuffs from blade use.:(
 
Yeah, those were my knives (thanks Alan). Yes the open front sheaths are easier to clean out... and my new closed kydex sheaths all have a cleanout vent at the tip so that you can use compresses air or water to flush out the sheath.

The whole scratch issue has been around since I first introduced thermoformed Kydex sheaths in 1982. And I still feel the same way about it. Kydex is for USERS. If you care about scratches on the blade then you're a collector, not a user and you probably should not be getting kydex. If you USE the knife it will get scratches anyway.... so those from the kydex will be immaterial. That said... you can minimize the effect by stonewashing (abrasive tumbling) the blade. This gives a very fine pattern of scratches (unlike bead blasting which is a fine pattern of pits) and makes the kydex scratches blend in almost imperceptibly.

But Kydex certainly has a place when it comes to EDC...

Here is a Haiku for you... this is what I put on the back of my T-shirts:

The only knife that matters
Is the one you have with you
At the time

It matters not what gorgeous knives you have at home sitting in a case in perfect condition with no scratches... it ONLY matters what knife you have with you... and can get to fast... when you really REALLY need it. Kydex scratches??? Bah! Humbug!
 
That would be the final word on ths subject it seems. Thanks for that, and of course for Kydex as a sheath making material. Quite a hefty contribution to the community.

On the subject of haiku... I, along with millions of non-Japanese, was raised to think of haiku syllabic structure following a fairly strict 5-7-5 pattern. So to exercise the pedantic, here's an interpretation of yours in that pattern:

the important knife
is the one you have with you
when it is needed
 
Ah yes... well... I struggled to force the concept into the 5-7-5 format, then realized that it wanted to flow more naturally in 7-7-3. Hopefully I may be forgiven that poetic lapse! ;) And besides... others might claim that it's not a "true" haiku because it does not contain two distinctly separate phrases but is rather one continuous phrase... a complete sentence in fact. Oh well! "Pen and sword in accord" as they say...

Here's the graphic that is printed on the back of the new Tee Shirts (which will be available at the Russell show). I wanted an iconic rather than a realistic portrait of a knife... and tried the technique of using a brush and working quickly... three strokes... swish, swash, swoosh! I did it something like a hundred times, used up a big pile of paper, and then chose this one as the one that most closely approached what I was looking for. I usually don't paint, so my wife (an art teacher) had to get firm in order to get the brush in my hand. It was an experience! I scanned it and stuck it on the shirt.

The shirts are pocket tees, 100% cotton, with the Maringer Custom Cutlery logo on the front pocket, and the Haiku graphic on the back. Colors Black or dark Navy with Khaki printing.
 

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