Sheath talk: Need ideas for positive retention

[Roamad]

Hoping the experts can help with this one. I'm making a knife for a customer who is a kayaking guide. He wants the knife to be attached inverted on his PFD so it can be withdrawn one-handed. I'm worried the usual Kydex retention strategies (molding and friction) won't be enough to hold the knife under these conditions. So I'm trying to find a simple "positive retention" strategy, for lack of a better term. I'm thinking something like a thumb break on a holster, or a maybe a simple spring loaded clip that would engage a notch in the blade tang or handle.

Recently I came across an older Gerber design used on the Blackie Collins designed Frisco Shiv model and others. It was like a grip safety, where you actually squeezed the grip to disengage a clip on the sheath to withdraw the knife. I love this idea, but it's probably to complicated and fiddly for me to construct and I don't know how rugged it really is:

Anyway, I'm looking for something easy to build and reliable.

Any ideas appreciated!

 

[Cody Hofsommer]

Well this might do better in the sheath subforum. I'm not kydex expert, but I have done a few, and I would think there would be plenty of retention of you designed the knife with that in mind. Just give it something to hold on to.

 

[Stacy E. Apelt - Bladesmith]

I'll move it to Sheaths.

 

[brettn]

I've been in the same situation with dive knives. Ultimately I came to the conclusion that even if I came up with a good solution, it would be hard to compete with production knives that were readily available. This doesn't answer your question but I thought I would share anyway.


Sent from my iPhone using Tapatalk

 

[sheathmaker]

The thumb break snap set up is probably the best solution, that you could duplicate easily in your shop. Good molded Kydex is probably more than safe enough regarding loss and would fit the other parameters you have in mind without any additional external retention devices.

Paul

 

[Roamad]

Thanks for the replies so far -- and thanks for moving to "sheaths" (forgot about that subforum option).

I'm liking the thumb break option. Reminds me that I actually made something similar once for a small nylon pouch for a folding knife, and it worked quite well. I'd love to see pix of how others have done this for a fixed blade.

Is there a way to ensure the thumb break folds back adequately so the knife can be put back in the sheath one-handed? I've seen this done on some sheaths with small bits of bungee. But again, I want to make sure this can withstand being around water and sun all the time.

With that in mind, can someone point me to a good source for marine-grade snaps (i.e. genuine stainless or brass) and other hardware for sheath-making?

 

[WhiteKnuckle]

Is there a way to ensure the thumb break folds back adequately so the knife can be put back in the sheath one-handed? I've seen this done on some sheaths with small bits of bungee. But again, I want to make sure this can withstand being around water and sun all the time.

With an inverted carry I don't think this should be an issue. You're going to have gravity pulling the break strap down out of the way.

I'd like to add that you should make the sheath a standard retention sheath and then add the thumb break to it, this way the knife can be put back in one handed and stay put while the break is reattached. Basically always assume that the owner is going to have the other hand full with his paddle, so the whole process, not just the draw, needs to be one hand capable.

 

[Horsewright]

Weaver has stainless snaps.

 

[John A. Larsen]

My Finnish Knife making friend, Pekka Tuominen, made me a Kydex sheath that has a dimple, that fits into a hole (depression) in the handle of the knife. Tight fit and the dimple in the hole makes it quite secure. John

 

[Roamad]

Thanks for the additional thoughts and the snap source.

JAL: I love the "dimple" idea. This could work if I include an adjuster on the sheath to accommodate loosening up.

 

[Roamad]

Thanks for the additional thoughts and the snap source.

JAL: I love the "dimple" idea. This could work if I include an adjuster on the sheath to accommodate loosening up.

 

[Mahoney]

Some years back AG Russell sold a line of plastic sheathed knives...Deer hunter, trout and bird, hunter's scalpel, that all used the same retention method. The front of the plastic handle was shaped into a finger guard that fit into a rectangular hole in the edge side of the sheath, There was a spring loaded post on the other side of the sheath. To remove the knife from the sheath you pushed the post with your thumb and the knife would tip a little in the sheath and come out. There are lots of pics out there on the net of the knives and sheaths. I had a couple of these knives and the retention was very good. The spring loaded post might be a challenge to fabricate but this might inspire some other ideas

 

[Roamad]

Thanks Mahoney. That's one I hadn't heard of. Some Googling revealed that AG Russell still makes that knife/sheath package. It's called the "Thumbolt" sheath (patented, of course) and they claim it's the "saftest in the world." It was actually designed by Blackie Collins. Seems he had a thing for sheath retention tricks!

 

[stitchawl]

Have you considered rare earth magnets? I embed two magnets taken from old hard drives in my inverted sheaths, and never had a complaint about shake-out, even when jumping down from a 6ft wall. These hard drive magnets are very thin but cover a wide area, and can be downright dangerous if you happen to catch your finger tip between two of them! Extremely powerful! I've not found anything like them being sold separately. The rare earth magnets sold tend to be fairly thick in the larger sizes.

 

[Roamad]

Never thought about magnets -- didn't think they'd be strong enough. How do you "embed" them exactly? And do I need to go looking for a particular kind of old hard drive?

 

[LX_Emergency]

Have you considered rare earth magnets? I embed two magnets taken from old hard drives in my inverted sheaths, and never had a complaint about shake-out, even when jumping down from a 6ft wall. These hard drive magnets are very thin but cover a wide area, and can be downright dangerous if you happen to catch your finger tip between two of them! Extremely powerful! I've not found anything like them being sold separately. The rare earth magnets sold tend to be fairly thick in the larger sizes.

Several Chinese websites sell these for not very much money.

 

[stitchawl]

Never thought about magnets -- didn't think they'd be strong enough. How do you "embed" them exactly? And do I need to go looking for a particular kind of old hard drive?

All full sized hard drives (not SSDs, though) have two large, (aprox 1"x 1/2"x 3/16") very flat magnets inside, one on either side of the base of the read/write arm. They are larger and flatter than any I've seen being sold in catalogs or on websites, and incredibly powerful! You will need a torx driver to open the case (don't forget the one screw that is under the label...) and remove the arm assembly. The magnets are glued to the brackets that hold the arm and will need to be pried off. To embed them, I usually just cut 'pocket' for them out of the leather, lay them in the pocket and fill in around them with 'ShoeGoo' rubber, and then cover with the liner leather. For Kydex you will have to mold a pocket for them. But be sure to use some sort of liner as they WILL scratch the blades. Two of these magnets will hold a full size Kabar style knife securely upside down, and not release it when jumping up and down. However, they may/will magnetize the blade to some extent so should NOT be used for EOD equipment knives.

 

[Roamad]

Awesome, thanks stitchawl. Don't know if this is the solution I'm seeking for this particular knife, but I definitely want to experiment with this. Now to find some kind of computer salvage place...

 

[aarongb]

Might be a little late for this, but you can try https://www.kjmagnetics.com, they carry all kinds of rare earth magnets including those surplussed from hard drives and other sources.