Super Glues

K

Kiddy Hawk Knives

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Aug 12, 2016
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Can I use Gorilla super glue instead of epoxy for attaching scales to knife blade? I'm new at this hobby so please let me know if this is an acceptable alternative to epoxy. Thanks for any advice.
 
You can if you just want to tack the scales in place while peening the pins, but super glue Just isn't strong enough ( cyanoacrylate is cyanoacrylate no matter what brand of super glue it is )
You're gonna need some epoxy 👍
 
I use superglue if I'm mocking handles up and need a temporary hold...but you definately need a long set epoxy for when your actually adhering the handle to the tang. Arcglass works well (same thing used for glass bedding rifle stocks
 
Many makers use CA glue for scales. With correct surface prep and fastners it will hold just fine.

Gorilla glue sets up to fast, if not positioned perfectly it will set to soon and leave a large glue line.

Go to a hobby shop and pick up some Bob Smith CA maxi cure and do good prep.

But CA glue can be a pain and clean up can be a mess unless you buy "un cure" to remove excess.

What I really like to use is BLade Bond Ultra epoxy. It is easy to mix, use and has a long cure time and is strong and never shrinks. It is only $13 and is a great product for the knife maker.
 
I put a set of thin scales on a pretty small fixed blade about 8 years ago with Gorilla brand super glue. That stuff is pretty strong and doesn't seem to get dry and brittle like other CA glues. I think I read somewhere that they use some type of rubberized polymers in there to give it some 'give' and impact resistance. It's pretty good stuff. I didn't even peen the pins. 8 years of daily use later it's still going strong.

It was more of a test to see if it would work. Not sure I'd trust it for a larger heavy use knife. But who knows? As was mentioned above, surface prep is everything.....probably more than the type of adhesive used.
 
J. Doyle said:
I put a set of thin scales on a pretty small fixed blade about 8 years ago with Gorilla brand super glue. That stuff is pretty strong and doesn't seem to get dry and brittle like other CA glues. I think I read somewhere that they use some type of rubberized polymers in there to give it some 'give' and impact resistance. It's pretty good stuff. I didn't even peen the pins. 8 years of daily use later it's still going strong.

It was more of a test to see if it would work. Not sure I'd trust it for a larger heavy use knife. But who knows? As was mentioned above, surface prep is everything.....probably more than the type of adhesive used.
Click to expand...

Huh, cool and good to know! I use gorilla super glue when I mock up handles and need a temporary hold...and can typically break it off pretty easy. It may be that I'm only using glue on certain parts on the tang and not the whole thing. Now I'm going to have to try it, you have me intrigued now!
 
While the bond strength may seem more than high enough, the shear strength is very low. Use a good structural epoxy and you will have both strengths as well as lots of time to place and adjust things.

I never read of anyone gluing their fingers to a knife with epoxy :)

Excess epoxy wipes away cleanly with denatured alcohol until it is cured, and any cured resin is removed with acetone easily. CA will only dissolve in acetone, ands may still leave a sticky film after it is removed, requiring a second clean-up.
 
Epoxy is more flexible and can take much longer to cure - which is preferred to give the handles some resistance to shock and impact. Super glue is too brittle for anything long term unless you pean pins through the scales, in which case the pins will be holding the scales on as opposed to the glue.


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When you use pins, corbys, tubes etc. The scales are not going to move and the CA glue will hold.

As will all glues surface prep is key and the use of mechanical fastners are holding the scales.

Do not be afraid to use super glues, some of the top makers are using it as well as locktite products to hold on scales. They just do not have the time to wait for epoxy and the CA glue gets the project moving.

I have used both CA and Epoxy and have had zero problems when done properly.

I like the blade bond epoxy better because it gives me time to move stuff in place, install pins, corbies ext. CA sometimes set and then you find a problem and you need to take hammer to remove the scale LOL, been there done that.

But if a maker wants to get serious using CA, do it right and get Un Cure and Insta Cure to use with the CA.
 
Lets see, with about 15 years of using the thick CA to put on scales exclusivley and zero
failures- guess I'm just lucky.
Ken.
 
I have seen the literature on Master Bond. It is the only reliable one part epoxy I know of. The two part systems is a very strong structural resin.

I'll try and explain what makes on resin better than another in my opinion. I won't go into covalent and adhesive bonding, but suffice to say that the way molucules of resin grip the surface has a lot to do with bond strength.

CA - cyanoacrylic resin - is a surface bonding resin. The curing is a process of polymerization. The polymer grips the surface of the host material as it polymerizes. This reaction is caused by water molecules on the surface of the bonded materials as well as the air humidity. The only strength of the bond is in the surface junction. The actual polymerized resin is an acrylic - AKA plastic - that is very weak. Such bonds ned to be very thin to have strength. This allows the polymers to attach to both sides of the bonded items with a single polymer strand. Any excessive distance, and the space between the surfaces is filled with acrylic. The surfaces need to be smooth, very flat, and in a very close fitting alignment. The surface does not want a rough texture, as this would interfere with the polymerization path. 400 grit is probably just right for CA bonding. The one pus in a CA bond is that over clamping isn't an issue, as there is rarely enough time to use clamps. Finger pressure is about all that is needed. The negative is that there is not much moisture in steel. For wood to wood bonds, CA is superb, but for bonding to metal of other non-pourous materials it isn't optimal. Also, CA is hygroscopic, even after curing, and will slowly break down with age. How slowly is hard to guess. There is very little difference in CA glues beyond how much carrier is added to keep the cost down. Some higher grade CA glues have some beneficial additives like rubberizing compounds.

Epoxy cures by chemical reaction. The product formed is fairly strong. In structural epoxies, the joint is often stronger than the joined materials. This joint requires a somewhat rough surface for the resin to grip, and a certain spacing to allow a physical presence of resin between the surfaces. Over-clamping is the major cause of bond failure. Quality structural epoxy resins have a very long bond life, and are fairly impervious to moisture. 100 grit is just right for epoxy.

This is not to say that a properly applied CA scale will fall of tomorrow, or that an improperly applied epoxy bond won't fail in a short time. The point is that with all things done right, an epoxy bond is stronger and more permanent than a CA bond. Those happy with a CA bond and who use the proper application are almost surely OK with their knives as long as there is a shear strengthening fitting like pins or bolts. Those using a structural epoxy and using the same degree of surface preparation and application will likely never have to think of a handle failure happening. A shear strengthening fitting is still important.
 
DB731 said:
I know JB Weld likes to throw around the 3960 PSI figure a lot, but it would appear the shear is a lot less: http://chemistry.stackexchange.com/...e-maximum-pressure-that-jb-weld-can-withstand

I was surprised to learn that apparently the strength of the bond (at least lap shear) increases with decreasing adhesive thickness:

https://www.researchgate.net/public..._Type_and_Thickness_on_the_Lap_Shear_Strength
Click to expand...

Correct. the film thickness is important. Too much and the resin breaks, not the bond. There is a larger margin for the thickness of the bond when using epoxy than CA because it is more elastic.
 
In my experience the quicker drying the glue the more frustrating...I can't personally work fast enough with 5 minute epoxy and have ruined blades with it before...I switched to 30 min epoxy. It has the strength that super glue does not have and enough working time to work at a comfortable pace.


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The only time i use CA "superglue" is when working with rubber handles. It seams to work really good for that but I'm now re evaluating this because a kitchen knife I made for the wife had a CA glue joint fail and the rubber lifted up. This is the first time this has happened so I'm wondering if my surface prep was off. But any other scales or handle material get epoxy or the good ol foaming gorilla glue. But that being said I never really trust the glue but I do trust mechanical fasteners and when used with an epoxy it's hard to beat.
 
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