Hidden bolster pins

G

Guy Thomas

Joined
Feb 1, 2000
Messages
1,370
I've been thinking about how to attach damascus bolsters to fixed blade knives without having the pins show. I know one way is to use hidden pins with a pressed fit along with a sealing substance like epoxy or JB weld.

Do you think there would be any advantage to using threaded stock larger than the holes drilled in the bolster material for the pin stock? (My thoughts are that the threads would crush as the bolsters are forced on to them creating a hooking action that would resist mechanical withdrawal of the pins from the bolsters). The holes in knife could be drilled and tapped to fit the thread stock allowing you to leave a fixed amount of pin protrudung from each side.

What do you guy's think? Is this just overkill? (I often tend to make matters more complicated than they need to be.) Is a regular pin, say one/thousandth of an inch larger than the pin hole, the simplest solution to the damacus or mokume bolster problem?
 
The threaded material might be too hard to conform to your bolster material very well. I think I would cut the pinning stock a little longer so it will expand when the bolsters are compressed and would stay with material that will does that easier. Brass or nickle rod.

Roughing up the pinning material and some good epoxy or JB and you will probably have a tough time getting this to fail. I am sure some of the other guys have some better plans. Let us know how this works, of course you will have to tear it apart to find out:D Terry
 
Guy I like this idea. But I have a concern. Wouldn't the tight fit cause some of the pin or bolster material to swell and prevent a close fit of the bolster? How would you get around this?

And how would this work...choose the bit, I guess, sized just smaller than your pin stock. Okay, I get it.

Dave
 
The last fighter that I made I put Motorcycle chain damascus for bolsters with 1018 pins and you can hardly see them after etching.
 
George you're right, the pins blended in pretty well with the chain damascus on that knife. I remember seeing it when you posted it here.

The problem comes when you want to use a piece of mokume or nice twist patterned damascus. The pins stick out like sore thumbs.

One solution is to treat the full tang knife like a folder and use screws. It's not an elegant solution to me, though I have seen a few knives where it worked quite well with the overall look of the knife.

Terry, I like the idea of leaving the pins long and as they are crushed in the pressing action they become shorter and wider but you'd have to get the pin length exactly right and they may not crush and expand the same from side to side, but I imagine enough pressure on the pressing would fix that.

Dave, that's right my idea was to have the blind holes in the bolster material slightly smaller than the outer diameter of the threads of the pin. The pins could be left shorter than the depth of the hole so you'd be sure the bolsters would snug up to the blade.

My big concern though is that the threads might not compress from side to side equally and the already shaped and etched bolster might end up askew after the pressing.

Here's a thought though. Tap the holes in the knife and tap the blind holes in one bolster only. Thread half the pin stock and attach that bolster by screwing the pin through the knife blade into the one bolster. Then the other bolster could be pressed onto the unthreaded pin stock. Hmmm, I think I'm thinking too much.

The real solution to this is forget about making full tang knives and go to mortised handle construction with guards instead of bolsters! I just have my first damascus billet still laying around here and I suspect half of it is only going to be any good for bolster material!
 
On a few occasions I have done this. Instead of pins, I used screws.

On the inside of both bolsters (the side that fits next to the tang) I drilled holes but not all the way through. I then used a dremel tool and made the hole have the shape of a mushroom. The sides of the hole were "wallowed out" without making the opening or the bottom of the hole have a larger diameter. Its hard to explain but I think you get the picture.

I tapped the holes in the tang where the pins that attach the bolster are. I then cut off some screws where I would have 3-4 threads protruding out both sides. I believe I used 10-32 screws but am not sure about the size. Almost any size screw will work. This was on a larger knife. (The smaller the screw, the more threads that need to be exposed.) I then epoxied the bolsters on with Shafting Epoxy from Golfsmith. JB Weld would work as well, its just thicker. Make sure that you get the expoxy in the holes in the bolsters. I then used a spring clamp until the epoxy was setup.

I would also recommmend getting the bolsters finished as close to "finished" before attaching them. To get the excess epoxy off, use WD40 or lacquer thinner on a rag or paper towel. Terry Primos has a very good tutorial on his website concerning attaching a guard that also includes a section on epoxy cleanup. His tutorial at the link below.

Solderless guards

If you do attach the bolsters in this manner, rest assured, they aren't going anywhere.

C Wilkins
 
Bingo! That's the perfect solution! The bolster line up perfectly to the tang because the diameter of the hole matches the outer daimeter of the threads of the pin and the epoxy forms an internal pin "head" that also adheres to the threads of the pin. You'd destroy the knife trying to get the bolsters off. Thanks!
 
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