Hidden pins - a structural question

Daniel Koster

Daniel Koster

www.kosterknives.com
Knifemaker / Craftsman / Service Provider
Joined
Oct 18, 2001
Messages
20,978
Are hidden pins as strong as full width pins?

(See diagram below for visual explanation)



I'm sure there is some difference, but I wonder how long the pin really needs to be in order to provide 80-90% the strength of a full-width pin.


I'm sure it also depends on the handle material, pin material, glue used, tang style, etc.


For the sake of argument, let's assume the following:
  • the handle material is stabilized/strong
  • 2 hidden pins - 1/8" diameter
  • the blank is a typical hunter-sized blade - 1/8" thick, either full or hidden tang. (for the hidden tang, there would still be 2 slabs, just cut to match)
  • Glue-up is either JB Weld, 2ton Epoxy or Acraglas.



How much strength is really being lost by the pins not extending fully to the outside of the handle material?

Dan





attachment.php



1 = Full Tang, Full Pin
2 = Full Tang, Hidden Pin
3 = Hidden Tang, Full Pin
4 = Hidden Tang, Hidden Pin
 
My personal guess is any strength loss, if any, would be unnoticeable or unmeasureable. I can imagine handles made in either manner would be extroardinarily hard to make fail. My opinion only.
 
I imagine that not make a big difference...
But you can improve the force of your hiden pins:

By using a threaded rod instead of pins. The epoxy will have a better bounding on a more grip.

You can also carve (with your dremel) the hole for the pin to make likes on
the image below.In this ways, that creates a epoxy rivet which cannot leave the
hole any more.

And sometime, when I do not use threaded rod, I smash the heat of the pins
with a hammer to make a mushroom head on two side of the pins.

Alain M-D

hidenpin.jpg
 
If the two ends of the pins are not peened, then it is only the glue on the surface of the pins that would help resist a force that is trying to tear the scale off the tang. The surface area of the pins is going to be quite small compared to the surface area of the tang so the pins will add little strength. Using grooved or threaded pins would improve this just a bit.

If a force is applied that would shear the scale off the tang, then the pin would help resist this force. One should get this benefit as long as the scale material was "strong" and the pins are not too short.

From my past experience with adhesives, it probably makes more of an improvement to choose an appropriate adhesive (strong, does not break down over time or with high heat, etc.) and ensure that the surfaces are really clean. If the scale material is not "strong", one would leave a layer of it stuck to the tang and the pins when a force is applied to the handle.

Phil
 
(Looks like phil was typing while I was, but I'll post anyway.)

I personally like hidden pins with Acraglas. Hidden vs. non-peen, you're better off with hidden. But Hidden vs. peened? i'd have to give the edge to the mechanical hold of a peened pin. Here's a picture of pins that go all the way thru so show what I'm talking about:

pins.gif


A peened (flared) pin is going to hold the material even if the epoxy fails. Practically speaking, if the epoxy fails you'll have more problems than the handle coming off - leaking and rust comes to mind. Also, acraglas is going to outlast any natural material. So, the material would be gone before teh acraglas.

Just my thoughts,

Steve
 
Originally posted by Alain M-D
I imagine that not make a big difference...
But you can improve the force of your hiden pins:

By using a threaded rod instead of pins. The epoxy will have a better bounding on a more grip.

You can also carve (with your dremel) the hole for the pin to make likes on
the image below.In this ways, that creates a epoxy rivet which cannot leave the
hole any more.

And sometime, when I do not use threaded rod, I smash the heat of the pins
with a hammer to make a mushroom head on two side of the pins.

Alain M-D

hidenpin.jpg
Click to expand...

I've done mine like the middle picture above and have never had a problem.

C Wilkins
 
When I get to thinking about stuff like this, I go back to basic thinking patterns. What will this modification add to the overall 'package'? Will this (hidden pin) make the knife more valuable, attractive and last longer? Will it perform better, worse, or about the same? Is the extra time and trouble learning this new method worth it in the long run for my knifemaking career? Is my current method pleasing and mechanically sound in practice? Lots of questions, I know.

My point is this; why hide a pin when it's even remotely possible that it won't do it's job? I have to ask myself how I would feel about seeing and handling and using a knife without any visible pins in the handle. The ABS requires a visible pin and thong on all test knives that will be used to chop and slash with and there's a reason for that. Seeing the pin gives a fellow confidence that the knife isn't going to come apart at a bad time and cause someone to get hurt.

When I see a finished knife without any visible pins it just makes me wonder why. Why no pin(s)? And glued pins? Don't get me started on those. Pins = peined. Period. For me, anyway. And yes, I know, there are some world class knifemakers out there that rely totally on epoxy with no concern for pins at all. And the knives seem to hold together fine. But if you think about it, a simple peined pin or two will take all the guesswork out of the longevity of a knife/handle. If it comes out of my shop it has at least one visible pin that goes all the way through the tang and handle. It helps me to sleep at night.
 
Ever since I discovered EPOXY the pin strength problem disappeared..with thousands of pounds per square inch gripping power on properly prepared handle and tang materials the pin no longer has any use except to act as a shear pin in case of lateral shear of the joint line. Just remember to rough up the pin or use already rough material like threaded rod so the epoxy gets a chance to get into the hole along with the pin.. a tight pin in a hole will wipe off all of the epoxy and there will be little grip in the hole itself.
 
I agree with you George. Epoxy is wonderful stuff and really makes our job much easier. But that wonderful bond goes away very quickly with the right amount of heat, flex or the right kind of shock to the blade or handle. Now I know that we're not glueing handles onto crowbars, but lots of times a heavy knife will be asked to do some pretty demanding things by unreasonable knife owners. I've done it myself and I know better. I've seen the epoxy let loose on more than a few knife handles. Especially full tang knives with tapered tangs. Fortunately I've only had one knife come back with handle problems and that was the first knife I ever sold. The handle flexed (that's all I could figure out) when the knife was dropped on the ground and the bone slab split across one of the pins. I know, bad example. That was a long time ago and I've learned alot since then.

But I'm still wondering where the glamour is in a hidden pin and why folks go to the trouble to hide them? That's what I'm curious about George. Being a knifemaker, I just wonder about the wisdom of that practice, is all. Is it a customer driven thing or is there more to it's functionality than I'm picking up on? Hey, I like to learn new things and if I'm careful I might just learn something here.
 
Hey max! Long time no chat!

I think that hidden pins are alluring because they are hidden! There is something quite attractive of a handle that shows no signs of how it is held onto a knife. I am glad this thread was started, as I had the same questions. I want to use hidden pins for aesthetic reasons as long as it doesn't adversely affect the integrity of the handle.
 
I agree with George but also barb my pins and hollow out
a space for the epoxy.

as far as yes or no to hidden pins or not
if the customer orders it with out pins showing this would be
one reason
as I did on this one
gray150.JPG
 
I notice you still have pins on your bolsters and pommel Graymaker. Why not hide them too? I could show you how to hide them without making them go away but that would require a shop visit. I know, if making knives was easy, everybody would be doing it. He he.
 
Acra glas, like Steve said, is stronger than the handle material. I use nothing else, and usually use hidden pins. Nothing has ever let loose, and I am 100% sure nothing will. I even 'glassed a couple of oak burl handles with an oil finish onto a machete. Three or four hard use years and the slabs are tight as ever, even after being banged around in the boat and used for cutting duck blind cover,plus being left out in the weather.
 
Max
I know how and thanks.. I've been making a very long time now. I just can't spell well..:(
this one the bolsters have hidden steel rivets they will not move..

those were an after thought your seeing,
you can't see it but your looking at
brass metallic inlays there to look as pins
as a contrast to trying to hide pins..very easy to do. :)
 
I only have a couple of models with hidden pins, for the most part the market expect the pins to be visible so that is what they get.
 
Graymaker, maybe I should set up a shop visit with you. I haven't been making knives all that long but it's all I do now and it's how I make my living, such as it is. Would you be willing to put up with me for a day or two? I've followed your postings and admire your stand on the art of knifemaking. If you'd share a few secrets with me I'm sure we would both come out on the long end of the stick. I may have a few secrets to share my ownself. Who knows? Are you game?
 
Not a problem Max I love guys coming over
but I will warn you I have no secrets I let it all hang out..
I'm learning every day...some of the guys in the club come
over too and I think it's the greatest thing to
share what we know. I"m interested in other ways people
do things and trying to improve on everything I learn.
it's what it's all about I think..:)
I really like the hammer-ins we have for the same reasons.
you or anyone are welcome here anytime
I'm at least 90% full time and most always here..
let me know when we can do it...
 
WOW! I posted that before I noticed that you live in Maine. Mapquest tells me it's 1,858.17 miles with an average driving time of 30 hours and 57 minutes. He he. It may be a good while before I manage that trip. My old shotrod might make it all the way to Little Rock if I baby it along! :D

I'm like you Gray. I love having visitors in the shop when I'm not covered up with work. I just had a fellow come for the second time and he's a real hoot! He forged a damascus blade a few years ago in a workshop type class and now he's trying to finish it up. It's amazing how some people look at things. He kept trying to pay me for the help and I kept telling him no, that's not how I do things. It's a pure joy to share what I know with someone who really has a desire to learn and I always wind up learning more than I'm teaching anyway. It really makes me pay attention to my processes and techniques.

Anyway, I appreciate the open invitation and if I ever get the chance to take you up on it I sure will. My shop is open too and if you ever get the chance I'd love to have you for a visit.
 
I just may take you up on that invite I have an old navy buddy that lives in littlerock I could kill two birds with one stone .

there is a lot to be learned just by teaching. and fun... :)
 
Thanks for all the great discussion, guys.

...pardon me while I let loose some steam...


For me, pins can be an interruption to a beautiful handle material. On certain knives, they have their place. On others, it gets in the way.

IMHO, there are not enough makers that actually design where the pins should go, what they should look like, etc., and then incorporate it into an overall idea to integrate the pin. When I see a knife handle with a brass pin smack in the middle of it - it makes me wonder if the pin placement was really thought about, or if it was just stuck there because..."well, just because." ("the blade made me do it..." ;) )

I understand the idea that it demonstrates sturdiness and can't disagree with that. However, if it's a matter that is simply solved by explaining to the customer the strength of a hidden pin being very close to showing the pin, then the freedom to be "pin-less" seems to greatly outweigh the "sturdiness look" (especially when done as mentioned above - threaded rod, etc.)

Personally, putting in pins drives me crazy because it's such a limiting factor on designing a beautiful knife handle. I think that's why most of mine have been hidden-pin, hidden-tang knives. However, I now have a few full tang projects I'm working on and I'm reluctant to add pins.


You don't feel your house is any less stable if you can't see all the nails and bolts...


Two more reasons not to "show the pins":

1 - Structure = Wood, bone, horn, etc., all "move" and metal doesn't - leading to cracks, materials becoming loose, or forcing me to use stabilized/synthetic materials.

2 - Aesthetic = there are literally hundreds of types of handle materials, shapes and sizes, and yet only a handful of pin types: brass, SS, NS, copper and misc. mosaic. Your ability to color-match is limited and you end up having to match your materials to your pins, rather than achieving an overall aesthetic.



BTW, I'm not trying to "persuade anybody to the cause" - just venting my frustration with pins to see if anyone can help me settle this in my head.


I'm very glad to see a few makers chime in with good solutions. Thanks again for all the help.


Dan
 
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