Need Advice - Hidden Pins on full tang

MTBob

MTBob

Well-Known Member
I'm working on a kitchen knife and have selected a piece of beautiful Birdseye Maple for the scales. This piece of wood has great eyes coupled with brown tone marbling. I started to consider using traditional full through-tang pins. But, I'd like to not take away from the beauty of the maple figuring by having pins showing, it seems to me that the look of the pins would conflict with the natural look of the eyes.
So, I think I see how to use a transfer template to get matched pin placement on the inside of the scales (though the tang), using, say, brass pins that protrude about 1/8" into the wood on each side. I would also use multiple additional holes for epoxy through the tang to the scales for typical added bonding.
I've done some searching on hidden tangs and haven't found a lot of information. It seems that this is not a well accepted way of attaching scales. I can see on a knife that gets severe use , say a camp / bush knife, this design may not be appropriate. But, on a kitchen knife will this attachment method be suitable?
What are your thoughts / ideas?
 
I agree with John, just use the tang as the template.
How about a screw of some sorts for the pin? Lots of pre made ridges for mechanical bonding.
 
I'm assuming a full tang config. I generally do one side at a time. That way I only really have to get the hole placement correct once.

1) Glue up side "A"
2) Drill a limited depth hole into the scale on the other side - This gives you one side that can't be wrong.
3) Draw alignment holes on the edge of the tang such that they are visible with the side "B" scale in place. Transfer those marks to the scale
4) Using a ruler, square, etc., mark where the hole should be by lining up the marks.

I generally drill my second scale hole bigger and test fit everything to be sure it is nice and snug against the bolster (no gaps!). The bigger hole lets things move around to compensate for anything that is "off". Then just be sure to overfill the holes with epoxy. I also clamp from the butt to the bolster as well as clamping the sides.

Hope that makes sense.
 
Hi Bob,

I was just thinking this through on a current small edc build for myself with birch burl. It has pretty grain, but not super nice with eyes and swirls. I still wanted to give it a shot until I walked out there, got in a hurry, forgot about my plan, and drilled the pin holes all the way through my nice scales.... It was also going to be light duty.

Anyway my plan was this:

Drill three large holes in the tang (at least 1/4" - 3/8") and scales a short way into the scales
I wanted a large size so I could "carve out" a space for the epoxy to form a head inside the wood. (Help me with the right word for that).
This would give me essentially three "invisible pins."

I was also planning to put about eight 1/16" SS locating pins around the edge of the tang in order to have something else besides epoxy.
I would have also left a bur on the heads of the pins to help hold the scales - but then again birch is pretty soft. If that didn't work I would have tried a dull point on the ends.

I don't know how large you'd want to go with locators, if you went that route, but I found 1/8 g-10 to be very, very light.

I haven't found much online either. But what I have picked up online are the ideas of carving out ("recessing?") an area for the head and leaving a bur or making a point on the locators. Only I would dull it to keep if from splitting like nailing through old lumber.

As I re-read this I remembered - try searching "invisible pins" if you haven't.

Take care
 
MTBob said:
Thanks guys, great tips. That threaded screw idea is perfect.
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J. Doyle said:
It will be fine if you use good epoxy and proper surface prep.

Generally speaking, epoxy provides most of your pull apart strength and pins provide shear strength.

Use your tang as your template.
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Correct me if I’m wrong but if I’m picking up what John is putting down, using a piece of threaded rod in lieu of pins would actually be counter productive. Reason being a screw of equal diameter will provide less resistance to shear than a solid pin. That being the case your trading more “pull apart” strength, which is most likely in excess already, for less shear resistance which is what you most likely need more of in this case?
 
Kev said:
Correct me if I’m wrong but if I’m picking up what John is putting down, using a piece of threaded rod in lieu of pins would actually be counter productive. Reason being a screw of equal diameter will provide less resistance to shear than a solid pin. That being the case your trading more “pull apart” strength, which is most likely in excess already, for less shear resistance which is what you most likely need more of in this case?
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theoretically this is correct. But in practice I can not imagine an impact where the shear strength of a bolt / screw of any size would be an issue, especially on a kitchen knife. Consider that 99% of kitchen knives are made with sheet metal rivets and no epoxy whatsoever.
 
Kev & John Wilson
Just after drilling the tang for hidden screws, I saw your postings. Great comments regarding the practical need for added sheer strength using a screw-pin. And, certainly, the limited amount of improved tension force (longitudinal to the screw) gained seems insignificant compared to the tensile strength of epoxy.
Because I want to limit the length of the screw (or pin) that protrudes into the scale to about 1/8" (so as to not risk hitting the pin when contouring the handle), I have come to the same conclusion that whether the pin is a screw or a smooth pin, it really doesn't make that much difference. Only a few threads will be in the hole in the scale. Also, I use G-Flex epoxy, roughen the glue surface by media blasting the tang, and drill multiple matching holes through the tang, and slightly into the scale, for added adhesion.
I suppose adding pins of some sort is prudent, and - I know this heresy and against conventional knife design - but, I wonder, are simple glued through-pins of any kind necessary from a mechanical strength standpoint...in any knife? Certainly mechanical compression pins (Corby, etc) will add significant strength to a knife scale. But for the common EDC or kitchen knife, I wonder whether glued through-pins add much structural value.
 
On a knife I'd sell I would definitely want some sort of mechanical hold, ideally peened pins with epoxy. However, sometimes we go way overboard in sticking handles on a blade (which I'm not saying is a bad thing). I believe a knifemaker friend of mine has a garden knife he made for himself that gets left outside in Oregon weather. It is held together only with 5 minute epoxy and, if I remember correctly, has been out there for over a decade. Anyway, I'm just saying that a good quality epoxy will probably do the trick for a personal knife, but take what I've said with a grain of salt, I've only been making knives for half a decade, not long enough to see results.
 
MTBob said:
Kev & John Wilson
Just after drilling the tang for hidden screws, I saw your postings. Great comments regarding the practical need for added sheer strength using a screw-pin. And, certainly, the limited amount of improved tension force (longitudinal to the screw) gained seems insignificant compared to the tensile strength of epoxy.
Because I want to limit the length of the screw (or pin) that protrudes into the scale to about 1/8" (so as to not risk hitting the pin when contouring the handle), I have come to the same conclusion that whether the pin is a screw or a smooth pin, it really doesn't make that much difference. Only a few threads will be in the hole in the scale. Also, I use G-Flex epoxy, roughen the glue surface by media blasting the tang, and drill multiple matching holes through the tang, and slightly into the scale, for added adhesion.
I suppose adding pins of some sort is prudent, and - I know this heresy and against conventional knife design - but, I wonder, are simple glued through-pins of any kind necessary from a mechanical strength standpoint...in any knife? Certainly mechanical compression pins (Corby, etc) will add significant strength to a knife scale. But for the common EDC or kitchen knife, I wonder whether glued through-pins add much structural value.
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I believe that 99 out of 100 knives would last a lifetime with no pins at all. But as Alden points out, there’s always that 1 that has a scale pop off for whatever reason, and it will always be a customer’s knife.

I became a diehard fan of Gflex epoxy when I had to remove a scale once. I got the liners out of order on one side. Nothing I tried would get the handle scale to release. Realizing that I would have to grind off the scale, I decided to do some destructive testing since it was a foregone conclusion. With the pins driven out, I put the blade in a vise and tried to break the scale off with a huge pair of channel-lok pliars. All that did was chew up the handle.

I took the knife to the grinder and had to grind all the way to bare metal. Even the fiber liners had been sealed along with the scale into a monolithic mass.

So I will say that unless the epoxy has insufficient adhesion due to poor prep, the pins aren’t doing a whole lot. Crazy talk, I know. None of my knives has ever come back with a handle failure.
 
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On this topic, FiF kind of proves my point. J Nielson is often heard saying that he believes mechanical fasteners are what holds the handle on and epoxy is only to seal the handle. He often chastises makers who use epoxy and pins.

Then they proceed to take the knife and try to chop through a railroad track. Tangs break. Blades break. But I’ve never seen a handle pin shear or a scale pop off.

There are sailboats crossing oceans in hellish gales, boats with hulls and ribs held together by Gflex.
 
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