epoxy

Another good adhesive was Kommerling "Korapur 666", although there are others in the range, the German refrigerated companies Schmitz Cargobull semi trailers were completely assembled with adhesive with just a few screws to hold the assemblies together while the glue dried, it was slightly expanding and stuck metal skins to annodised aluminium frame components and porous insulation material with equal strength.
There was another adhesive, could have been the same, that bonded the plywood floor to the five bar or barley seed aluminum plate, a few times I witnessed lack of adhesion, usually due to driving fork lift trucks over the floor at the back, but not much considering the quantity of stuff they built.
 
Fellows, let the mods take care of this. Natlek has been warned. Don't reply to his comments and don't antagonize him. The mods have it under control.

To ALL of you, try to be more tolerant of others. Not everyone knows what some of us know.
 
There are lots of different types of forces that could break an epoxy hold. Compression, tension, shear, torsion, impact, vibration... Many of which can occur in multiple directions, and they can be combined in odd ways. There are test methods for each of these, and likely different performance metrics too. Real life breakages probably involve multiple stresses at once, or cumulated over a lifetime of use.

One method of glue up might be best for several of those stresses, while another might be required to resist others. That is why I think the glue pockets method exists, rather than just 2 flat surfaces glued together. It is certainly why people recommend pins of some form. But, who really knows what is better in real life performance? I don't. And no single engineering performance test can prove anything out to my complete satisfaction. Hitting it with a hammer a bunch of times is probably the best overall test anyone can find.

Stronger isn't always better. Sometimes a material needs to give a little, and sometimes it needs to resist giving too much. Just like the steel we harden it up to super hard RC, then temper it back to more useful levels so it doesn't shatter.
 
I read about bond lines and stuff, just thinking back to how I don't actually know how thick- specifically- the bond line should be. One of the data sheets I checked out had a suggested range of .005" to .02" bond line thickness, with a thinner line providing higher shear strength, and peel strength increasing at the thick end of the range.

also, I'm questioning my earlier statement about fasteners providing many times more shear strength than any bonding agent. I have a feeling that's not necessarily true, and that there is data out there about this very thing. That was me talking outta my ass, I'm going to own that one.
 
Lorien said:
also, I'm questioning my earlier statement about fasteners providing many times more shear strength than any bonding agent.
Click to expand...
If you’ve ever seen a tool maker use simple sewing thread and glue to make a ferrule, it’s a great example of how a comparatively weak substance spread over a sufficiently area can create a very strong component, equivalent to common metal ferrules.
… granted that particular application is hoop strength, but it’s an impressive example.

Epoxy is impressive stuff, even though I prefer fasteners.
 
hey, c'mon now! This thread is already problematic, let's keep it out of the gutter and leave 'hoop strength' conversations for W&C, m'kay?
 
Way-Barney said:
A few years ago now, in a commercial vehicle accident repair center, I used to get the guys to use 3m Panel bond to re-fix wings, door pillars sills etc. anything that we had to cut out and replace after a smash up even structural components at times. A few arguments ensued with the old timers who thought that spot welding everything together was still the best thing to do, I got the 3m rep in to instruct in the correct application of the products and explain how the manufacturers were using adhesives to assemble the vehicles in the first place etc It took me back to my welding days as the same fundamentals applied.
Surfaces to be joined must be Physically Clean and chemically clean.

Has anyone tried these "New technology" adhesives in knife handle assembly world?
Click to expand...
There are some really, really strong commercial adhesives out there … 3m VHB tape being one of them (apparently 3m sells a LOT of the stuff to manufacturers). However, mostly these things are used in a way where they are “hidden” ( ie underneath something and not visible). Vhb would likely hold a handle very well, but it has some substantial thickness (and would be visible), and is a little gummy … so you can’t really sand it…. Epoxy has the advantage that when fully cured it is *hard*, and sands and polishes well
 
Cushing H. said:
There are some really, really strong commercial adhesives out there … 3m VHB tape being one of them (apparently 3m sells a LOT of the stuff to manufacturers). However, mostly these things are used in a way where they are “hidden” ( ie underneath something and not visible). Vhb would likely hold a handle very well, but it has some substantial thickness (and would be visible), and is a little gummy … so you can’t really sand it…. Epoxy has the advantage that when fully cured it is *hard*, and sands and polishes well
Click to expand...
I use Devcon 2 ton epoxy, probably not the best but I have not researched it really, I have a couple of knives I made 20 yr ago which have seen pretty regular use, not constant but regular, and they have exhibited no issues for me.
Making a few knives here and there for my own use is incompatible with starting out on a research program. However, if like some prolific makers here who are doing dozens of knives at a time, I don't think I would be messing about making epoxy mixes. I would want a cartridge application system with a decent handling time and whack a couple of hundred knives at a time on a vacuum bed and have done with it. In my experience reps are falling over themselves to help even if you only bought 10 kilo a month.
 
I experimented with 3M VHB tape years ago. It comes in various thicknesses. from .005" to .100" It is surprisingly strong. I used the .010" tape on some fillet knives with thin tangs and blades. The handles were a greyish micarta. The seam was almost invisible.
I have lost track of those knives, but don't know of any of the six that had a handle failure.
 
David Mary said:
And a class act to boot. (see what I did there 🤣 )
Click to expand...
I'll see your boot, well my boot, see I did it too:

UrExpU6.jpg


And raise ya two points:

XRM8nTt.jpg


Way-Barney said:
I use Devcon 2 ton epoxy, probably not the best but I have not researched it really, I have a couple of knives I made 20 yr ago which have seen pretty regular use, not constant but regular, and they have exhibited no issues for me.
Making a few knives here and there for my own use is incompatible with starting out on a research program. However, if like some prolific makers here who are doing dozens of knives at a time, I don't think I would be messing about making epoxy mixes. I would want a cartridge application system with a decent handling time and whack a couple of hundred knives at a time on a vacuum bed and have done with it. In my experience reps are falling over themselves to help even if you only bought 10 kilo a month.
Click to expand...

I did have several handle failures years ago with that particular epoxy. Right at the two year mark. This was a pretty common deal, enough that a well know ABS MS spent quite a bit of time on the phone with their engineer. What I read from the MS's writing of his talk with them was basically they built in some failure right at about two years so a guy would be buying more epoxy. After I fixed the 4 or 5 failures I had, I've never had another failure where the scales just fell off. Had a few broken or cracked scales but nothing falling off. Should mention of course that I did switch epoxies to fix em and never went back to the Devcon.
 
Last edited:
Stacy E. Apelt - Bladesmith said:
I experimented with 3M VHB tape years ago. It comes in various thicknesses. from .005" to .100" It is surprisingly strong. I used the .010" tape on some fillet knives with thin tangs and blades. The handles were a greyish micarta. The seam was almost invisible.
I have lost track of those knives, but don't know of any of the six that had a handle failure.
Click to expand...
That’s a cool idea. It‘s crazy what some of that VHB tape will stand up to. Were you pinning the handles too? I believe the surface prep is similar to most other adhesives in general but I think there are some metals (copper containing alloys?) that require special surface prep. Did you have to do anything special? It also needs a decent amount of clamping pressure over its area if memory serves me correctly but that should be easily achievable in a vice or something like a kydex press for an odd/contoured shape. Interesting…
 
The first two were an experiment. There were no pins. I sanded to 120 grit and made sure both the tang and micarta were dead flat. I cleaned them off with alcohol and applied the film/tape to the scales and then put the scales on the tang. I let it cure a couple days and then trimmed the scales flush with the tang. I let them sit a few weeks to make sure the bond was full and then whacked on the handles and tried to twist the scales off - nada. I tried to get the scale off one by batonning a knife blade between the tang and scale to start to lift it. If it was wood, I am sure I would have broken the scale before the tape let go. The other is probably somewhere in the shop as a sandpaper cutter.

I made six more with the tape and pins, which all worked fine. I gave them to fishing friends and have never heard back that one failed.

It taught me that the tape was strong, but I stayed with my preferred System Three resin because I figured the seal was better. On my knives, the epoxy is for the seal since I use mechanical fasteners. It has enough flex to hold up to any amount of use. For many years, I used the two-part 24-hour cure stuff from K&G. It is very good and dyes quite well. The main reason I switched to System Three is the shelf life is almost forever and it is available at my local woodcraft. That, plus you can choose the hardener to match the ambient temperature with the three different hardeners available. They will cover shop temps ranging from 32° to 90+°.
 
Yeah … I used the vhb tape to secure some solar electric panels to the roof of my rv. 3-4 years of direct sun, rain, wind, blinding heat, arctic cold … and not a sign they are beginning to looen. I am convinced that if I really tried to lift them that the fiberglass roof covering would rip off before the tape came loose. Incredible stuff.
 
Been using the G-Flex for years, but decided to give the System 3 a try, so bought a small kit from knifekits.
 
You must log in or register to reply here.
Back
Top