Kydex sheath press - affecting blade temper

Brock Cutlery

Brock Cutlery

Joined
Jan 10, 2015
Messages
1,673
Hey folks,
I'm just getting into kydex sheath making and was wondering if putting the knife in the press with heated kydex affects blade temper?
 
No. Kydex will melt before you get into temps that will effect the heat treat.
I stay between 300 and 325 degrees with kydex. Above 350 and your kydex could scorch, shrink, or change color.
Your blade is going to cool the kydex pretty fast that's why it's good to be really quick moving it from your heat source to the press. Hope this helps.
 
Thanks Josh, that does help. Do you put a layer of painters tape on yours, or just cold hard steel?
My first try I used the tape and it seemed to come out alright. I figured it would also insulate the blade a bit, but it doesn't sound like that's a factor.
But I don't really want a super tight fit on this as it's a kitchen blade, and this is more of a saya than a sheath.
 
I've thought about doing some kydex for kitchen knives for people that don't want sayas.
That's a good idea. I put two layers of the blue painters tape on each side and cut the access off around the blade.
There are others that do even more layers than that. The only reason I use two is if the knife is being carried handle down, the retention is still very good. Like you said, with a kitchen knife that's not necessary. You can always use a heat gun and relax the kydex when your saya is complete. I usually do this on every sheath just to get the fit I like.
 
I normally use one layer of painters but actually preheat my blade and foam with a heat gun before pressing. I think Aaron gough showed this in one of his videos. Helps not shock the pliable kydex with cold steel so you get that pretty outline of blade profile and the retention you need.
 
Hey Christo, I went with one layer on this one too. I have to say I don't like the idea of a heat gun on my blade, but I did hold it over my heated kydex press to let it just warm a bit.

Here is my makeshift press. I wanted to try the basics out before I build something nice.
Also pics of the kydex out of the press, and a second of the inside form in the kydex. Seems pretty good!


kydex1.jpg


kydex2.jpg


kydex3.jpg
 
This thing actually has decent retention (for the kitchen) based on the choil profile. Pretty pleased with that! :)
 
The tape will not effect retention, at least it shouldn't. A kydex sheath should be retained by the handle, or heel or choil. You don't want the kydex rubbing on the blade flats, or it will scratch the blade should anything get in the sheath. I've been thinking of making some kydex blade sleeves, with a little retaining clip that will retain the blade at the heel end.
 
Kevin McGovern said:
The tape will not effect retention, at least it shouldn't. A kydex sheath should be retained by the handle, or heel or choil. You don't want the kydex rubbing on the blade flats, or it will scratch the blade should anything get in the sheath. I've been thinking of making some kydex blade sleeves, with a little retaining clip that will retain the blade at the heel end.
Click to expand...

Hey Kevin,
I did a little research on the scratching. I don't want that. My sanding is lengthwise so it shouldn't show I think if it were to happen. I guess the same thing could happen with a wooden saya.
I plan to cover this with leather as I don't much like plastic from the artistic perspective.
I'll post some pics when this is done.
 
Kevin McGovern said:
The tape will not effect retention, at least it shouldn't. A kydex sheath should be retained by the handle, or heel or choil. You don't want the kydex rubbing on the blade flats, or it will scratch the blade should anything get in the sheath. I've been thinking of making some kydex blade sleeves, with a little retaining clip that will retain the blade at the heel end.
Click to expand...

That's a good idea. I think I'm gonna do something like that. I wonder what the best way to adhere a thin piece of leather to either piece of the kydex, on the inside? Leather cement? CA glue? Or maybe even an epoxy like G-flex.

You'd probably want to wrap the blade with a few extra layers of painters tape so that the fit wasn't too tight once the leather was put in place. You could also leave a space by the handle without leather, for better retention. With that in mine, you'd probably have to use a heat gun on the handle area of the sheath, with the knife in it, to compensate for that area being pushed away from the handle.

Oh, and of cleaning sanding grit from getting inside the sheath, I just put all the eyelets into the sheath prior to shaping/cutting off the excess. I DON'T flare them though, until the sheath is completely trimmed and shaped. I use one of those metal spring clamps to hold the two pieces together while shaping. Then I just take the two pieces apart, and then wash/scrub the insides real well. Then dry it, put the eyelets in, flare them, and you're good to go.
 
I think another maker on here used some kind of velvet like material on the inside of a sheath for a tanto or kwaiken a while back. I don't think I'd bother, since it seems that would be even more likely to retain grit, in a rigid sheath that is difficult to clean. I do like you for shaping. I'm thinking if a rectangular cover with the point end totally open. This would make cleaning easier. I'd form the cover "taco" style over a bar of steel slightly thicker than the finished blade. Eyelets on the open edge and attach a pivoting "L" shaped piece to retain the blade at the heal. This pivot would attach at the last rivet, closest to handle via Chicago screw.
 
Safariland uses a felt type material inside of some of their holsters. I ran one of their 1911 holsters for USPSA/IPSC, and it had it. It kept the finish on my gun nice and it was a real good holster. I think it had a kydex core, a thin leather outer layer, and the thin felt or maybe suede inner layer. Now that I think about it, it might have been suede. Felt seems like it wouldn't hold up very well at all. With higher polished kitchen knives you should definitely look into having a liner inside of your kydex sheaths. In my experience, even if you remove ALL the abrasive grit from the sheath, it will still scratch a blade finish. It's pretty troubling because kydex is definitely way softer than any blade steel. It happens nearly every time for me when I do kydex.

I just looked through some of my leather stock and found some thin leather from a real cheap Hobby Lobby scrap bag that I think will be perfect.

Sorry for derailing the thread. I don't think there's much of a chance of ruining a temper on a blade at all with hot kydex. As someone else said, it would melt before it got to the temp that would harm a temper. One thing you can do to get things exact is get one of those Non-contact Infrared Thermometer with Laser Pointers. Mine works GREAT for doing kydex. I also use a big pancake/egg griddle to heat the kydex. I try to get the griddle to around 250F-280F and then slap the kydex on. Then I let the kydex get to around 240F-250F, which I check with the thermometer. That's the temp where the kydex gets good and pliable. If you go much beyond that you get this weird shiny finish on the surface of the kydex. Results for any process are improved immensely by using a method that is measurable and repeatable. The laser thermometer allows that. It can also be used to check the temp of quench oil.

I have a heat gun, and they DO help sometimes. I try to always do things in a way were I don't have to use it though. I think one of those may be able to effect a temper if you leave it on high temp, and in the same spot on a blade. It would melt the kydex though before you got to the 400F point. Which most steels are at least tempered to.

Good luck!
 
You must log in or register to reply here.
Back
Top