Corby bolts + epoxy ?

One comment about installing the Corby bolts. Don't get epoxy inside the female bolt half. It will prevent the male piece from screwing in ( you can't compress a liquid).

When installing the female bolt, I put epoxy around the shaft and slip it in the scale, giving it a twist to spread the resin along the seat. I then spread epoxy on the inside of the scale, keeping it away from the bolt's threaded hole. Set the tang in place and do the other scale the same way, and set that scale on the tang/scale already assembled. Give each Corby a turn with a screwdriver to get them mated and tighten all slowly until just snug.
 
Hengelo_77 said:
Crushing H, please do explain more in depth
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Ok … a mini discussion on Adhesion – for those who are interested….

There are more aspects to adhesion, and types of adhesive joints – but I will limit this post to those that are most likely to affect the tang/handle joint. Ever wondered how people make stuff stick to Teflon (a specifically non-stick substance)??? Hopefully by the end of this will you understand how.

I will try to cover the following issues that might affect your handle joint to the metal blade (remind me if I missed one :

· Surface cleanliness
· Residual organic chemicals in the handle material
· Surface flatness
· Surface roughness
· Glue bond thickness
· Mode of failure (tension, shear, peel)

So – there are two major contributing mechanisms that make an adhesive joint work: chemical interactions and mechanical interactions.

Chemical interactions are just that: chemical bonds between the glue and the surface(s) being bonded. If the glue forms these chemical bonds to each of the two surfaces, and is sufficiently strong in its body, then you have a successful joint. An example of this type of glue is cyanoacrylate (Krazy Glue). A great limitation on chemical bond based joints is the need for surface cleanliness – you want the glue to have direct intimate access to the active chemical sites on the material you are bonding to. Anything that gets in the way – especially organic chemicals of the oily or waxy type will do two things: 1) physically get in the way on the contact of glue to the surface, and 2) possibly compete for the active chemical sites of each, and reduce the number of chemical bonds between glue and surface (thus weakening the bond). Also, over time, these competing chemicals can compete with, and undo, successful bonds between glue and surface. Thus the practice of cleaning a surface with an organic chemical like denatured alcohol, isopropyl alcohol, or acetone – which “dissolves” surface organic oils/waxes and carries them away, leaving the bare surface to be bonded to.

There is, however, a “gotcha” on this: many plastic/resin based materials contain residual oils and other chemicals in the bulk of the material that are not bonded to the plastic or resin. Thus, even if you can successfully clean the surface of that stuff, and successfully create a bond using a chemical-bond based glue, these residual chemical in the bulk will (not can) over time migrate to the surface where the bond has been made. These chemicals compete with the chemical bonds between the surface and glue – and can “undo” those chemical bonds between glue and surface (technically this is a chemical active-site competition – which is the underlying principal behind all chemistry). So it is entirely possible that a joint will be made successfully, but then fall apart at a later time. Time is the enemy here – it might take a month or ten years …but that migration of chemicals in the bulk to the surface will occur.

Any material that has significant organic compounds can be subject to this migration effect of residual chemicals in the bulk material. These materials would include: fully synthetic (resin based) handles like Kirinite, manufactured materials like Dymondwood, resin stabilized wood of any type, and, I would believe, any highly resinous tropical wood (even if not stabilized). Also, purely chemical-interaction based bonds between disparate materials are just not that strong. Many materials, like Teflon, just do not like to make any chemical bonds to anything else. So, especially under the right circumstances (Mode of Failure – will cover later) purely chemical-bond based joints will easily fail.

All is not lost though: the other contributor to adhesion is mechanical interactions.

(I think I will stop this post here and pick this up at a later time – gotta get to the gym and get some exercise!!!
This also gives you some opportunity to let me know if I am just boring you with this so I can stop…..)
 
OK Great, but C Cushing H. please do go on or even start a new thread, that's very interesting so far!
 
I'd second starting a new thread, this is good stuff to know, thanks for sharing!
 
Great thread! I use corbies or loveless with G-flex epoxy on every knife I make now. #paranoid

If you grind out a hollow in the tang and/or drill additional holes for "epoxy pins"... Does over-clamping (or over-tightening of the corby fasteners) really matter any more? I'm not saying that I attempt to clamp down hard on my handles, but I was just wondering since I've always thought that "just snug" or "not too tight" were slightly vague recommendations that could vary from person to person and knife to knife.
 
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Bill DeShivs said:
Or, if you peen your pins, you won't have any problem.
Knives were made for hundreds of years before epoxy was invented, with peened pins.
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Yep, exactly. This is how I have done my knives with pins. No epoxy, and no problems. The scales and the tang mate up perfectly. Peening makes everything nice and tight, and makes sure nothing is going to pop off. I’ve tried to pry my scales off with a chisel and hammer, and had to finally end up grinding the pins down first before I could get the scales off. Peening the pins works great.
 
Kimball_Knife_And_Tool said:
Peening the pins works great.
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Can you please elaborate on how you go about peening? I put a handle on a premade cleaver blank, used 1/4 inch brass rod for pins. Looking at this nicely sanded and finished handle with flush pins, i was quite timid with the ball peen ... seemed way too easy to miss and destroy the finish. Seemed to me one could use a punch ... but that would require three hands (one to hold the blade on the anvil, one to hold the punch, and one to hold the hammer). How do you go about executing this with just two hands?
 
Sorry for the crappy video.
You peen pins first, then finish them flush, and they don't have to be flush.
 
Bill DeShivs said:
You peen pins first, then finish them flush
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On the blade I made, my scales were quite oversize (in thickness) ... and did not have a band saw to rough down to size. so I had to resort to sanding down to thickness after gluing ... which left the (unpeened) pins flush......

So with your approach... you would need to have the handle pretty much shaped to near final form before placing the pins, gluing, and peening??? Is that right?
 
Cushing H. said:
Can you please elaborate on how you go about peening? I put a handle on a premade cleaver blank, used 1/4 inch brass rod for pins. Looking at this nicely sanded and finished handle with flush pins, i was quite timid with the ball peen ... seemed way too easy to miss and destroy the finish. Seemed to me one could use a punch ... but that would require three hands (one to hold the blade on the anvil, one to hold the punch, and one to hold the hammer). How do you go about executing this with just two hands?
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Sure thing!
I usually get the handle almost finished, but not totally. Then I cut some pins to the right size, and put them in. I'll have the handles placed on my anvil, then using a flat headed hammer, not a ball peen, I'll start mushrooming the pins. Aka, peening.
Yes, there is the possibility of slipping and maring the handles. It takes practice and skill like anything you do making knives. That's also why I don't totally finish my scales until after I've peened them.
Then yeah, after I've peened, I finish everything up. Making sure to not take off too much of the peened pins.
Sorry if it doesn't make much sense, I'm not the best at explaining something. I hope it helps though.
 
It does make sense - thank you. I have always thought about gluing the handles in place, with pins, then sanding down to size/shape. Seems like to do this effectively, you need to think in terms of sanding/shaping the handle scales individually to get them close, and then gluing up along with the pins (except you do not glue - right?). Just a different way of thinking about the sequence...

Thank you!
 
Natlek said:
Pins are cheap , use one set for shaping handle and other set /longer/ for final assembly and peening .
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Hmmm ... initial assembly with butchers wax on the pins (to inhibit epoxy adhesion), then punch out, and insert/peen the final pins???
 
On a fixed blade I do not like to sand the scales with pins installed.

I will epoxy on the scales and use pins, or bolts with nuts, covered in floor wax to index in place.

When the epoxy sets up I will remove the waxed pins, shape the handle and when completed I will taper the pin holes, insert pins and peen, then file and sand pins flush.

This way you do not burn your scales.

Here is a pict. Wax them up. Let the epoxy set and then remove. Clean out with drill and acetone.
FHc3WrH.jpg
 
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