Retention issues

[N.W. Gean]

Hello all. As those who frequent the "what's going on in your shop" thread in the knifemakers forums may have seen, I've got a couple knives that are ready for sheaths.

The problem is, I'm horrible at leather work. Every sheath I've made so far has either broken stitches or can't hold the knife to save its life. I'm chasing down the retention issue right now because I assume the broken stitches are from bad design. I think it's my welt design but I'm not sure.

How far should the welt be from the "beak" of this knife if I want the loveless style cam? I believe I saw a post by Horsewright saying he uses a space of 3/8" from the widest part (or beak in this case?) for a cam, but that is for a pancake and not a fold over sheath, unless the principle is the same?

Hopefully I don't have to scrap this piece of leather as I've wasted quite a bit this week . Luckily it's cheap 6 to 7 oz Tandy import leather, which I understand isn't great but it's still breaking my heart to screw it up.



Is it realistic to expect the sheath to hold the knife while upside down? I want the knife to be well protected against adverse conditions.

What's the prognosis, friends?

Thanks,
N.W. Gean

 

[Horsewright]

Ran out of time this morning NW. will answer tomorrow.

 

[N.W. Gean]

Thanks, Horsewright. No worries. I've been cleaning the house with the wife today

 

[Horsewright]

Welcome to Sheaths and Such NW.

First is it reasonable to expect the sheath to hold the knife while upside down? Absolutely. Watch this little video and have your sound on, I describe what I expect:

https://www.instagram.com/p/BtKcsUfjAeM/

The cam on your welt needs to be more acute. The biggest problem with how you have it drawn is that it never fully engages the knife because the tip of the knife bottoms out before the knife is far enough past the cam to really get all the way into the sheath if that makes sense. This picture shows what I'm talking about.

While these are pancakes the interaction between the knife and the welt is the same. The cam of the welt is more acute and there is a "pocket" once the widest part of the knife is past the cam. This pocket is what your welt and sheath design is missing. It's what is definitely causing your retention issues and probably some of your cut stitches too.

On a folded sheath I place the knife along the fold and then fold the top layer over. This will move the knife slightly into place. I hold the knife there and draw my welt line:

I will then check the fit of that with the widest part of the knife. This pic shows I wasn't happy with it. The little vertical marks are Dave code for fit the welt to the bottom of the line not to the top:

I much prefer too tight over to loose and I can loosen almost any sheath up with needle nose pliers and a rat tail file If I need too. I still don't always get them right and occasionally have to redo a sheath but that video shows ya what I'm looking for.

Hope this helps.

 

[N.W. Gean]

Hi Dave, thanks for the reply. If I am understanding correctly, by acute you mean pointy?

I have revised the welt to allow a pocket, and made the cam closer to the beak. Do you think the welt after the cam will inhibit the knife movement or will the spacing above the spine/below the sheath fold take care of that? Or does the cam need to be even more acute?

 

[Horsewright]

Hi Dave, thanks for the reply. If I am understanding correctly, by acute you mean pointy?

I have revised the welt to allow a pocket, and made the cam closer to the beak. Do you think the welt after the cam will inhibit the knife movement or will the spacing above the spine/below the sheath fold take care of that? Or does the cam need to be even more acute?
View attachment 1484779

I think we're good there because the knife will go in past the cam and settle into the pocket. If anything I'd probably move the cam a little further up the handle of the knife to give the pocket a hair more room for the knife.

 

[N.W. Gean]

Thanks! I actually put the sheath together yesterday before work. I messed around with tooling since I decided it was a prototype sheath and not what I want to give my customer. I surprised the heck out of my self with the stitch line though.

I agree with moving up the cam. I think it could stand to be more aggressive. Haven't wet formed, but I can feel the knife clicking past the cam, however, it is still rather easy to shake the knife out. Better than what I've made before, but certainly room for improvement.

In the 3rd picture the redline is what I'm thinking for a revision on the welt. A little more aggressive on the cam but a slightly wider mouth for easier insertion into the sheath.

I'm assuming that even the more aggressive cam should have a spacing from the widest point on the knife before the sheath is folded over, correct?