Which epoxy do you use, and why?

I've been using 30 minute slow cure from Midwest Knifemakers Supply. It's what was recommended to me a while back, and for the most part, it's worked pretty good.

I do a lot of segmented scales, and the 30 min stuff gives me plenty of time to get things where they should be before it's too late. I was reading on Insta Gram tonight, and someone made mention of some 30 second aircraft glue, made for work on airliners. It got me thinking. The 30 second stuff would be fast enough for me to get segments done individually and then glue them all together. Sometime the 30 min stuff takes too long, and things are still moving under pressure of the vices. That makes for some scraps, and a lot of time wasted.

Anyone use this 30 second stuff? Either way, I'd love to here some of your experiences with different epoxies.

Suggestions are welcome.



Thanks,

Don

I personally like time when it comes to epoxy. I would get so full of anxiety having only 30 seconds that I would probably end up gluing my scales to myself. I like using the 30 minute slow cure, Devcon 2ton or west systems.

There's lots of "likes" and "dislikes" when it comes to "epoxies". A couple of things that I have learned over the years.... 1. Most of the 2-part epoxies that are publicly available, are chemically engineered to start breaking down in 5-7 years. I discovered this the hard way...way back when I first started making knives, I used Devcon epoxy. At about the 6 year mark I started getting calls from clients saying "The handle on my knife is coming loose!" Long story short, I learned that compainies engineer expoxies to start breading down in 5-7 years....it's how they stay in business. 2. The vast majority of them, even those that are advertised as "waterproof" are not....more like mildly water resistant. With just a few hours exposure to water, many cured epoxies will become "gummy" and loose. 3. Shelf and hold lives: From what I mentioned in 1 & 2, its obvious that most hold lives are in the 5-7 year range, shelf life is generally 90-120 DAYS.

Ok, all that being said, a person is gona use what they have come to like and trust. For me, there are only two "expoxies" that I will use for knives.... My first choice is Brownells Acraglass..... 10 year shelf life, 50 hold life, and totally waterproof. Next in line for me would be West Systems Marine epoxy.... 5 year shelf life, and 30 year hold life.

A couple more things to keep in mind..... "fast set" 2-part adhesives have the shortest shelf and hold lives. The longer the cure time, the more stable and longer lasting the adhesive will be.

I use two epoxies in my shop… and Ed already mentioned both of them: Acraglas and West Systems.

I'll make a suggestion as what not to use and that's the "store brand" epoxies. Twice I have gotten some that when mixed as directed wouldn't cure. That may have to do with shelf life.

Doug

I'm not going to argue with anyone's statement about how long an epoxy bond is going to last. I emailed two epoxy companies with requests for industry links to epoxy life. Neither of them were able to produce links to actual epoxy chemical bond life. Raka Epoxy (fairly well known in marine area) responded with " To my knowledge the only thing that will breakdown epoxy chemically is the UV light. Epoxy itself is chemical resistant so most normal means to break epoxy down wouldn’t do much of anything."

The other company was West Marine with the following response in full from Thomas Pawlak; Technical Service with Gougeon Brothers, Inc. of West Marine Epoxy folks.

Hi Ken,
If the epoxy in a glue joint is isolated from sunlight and other forms of UV light, I don’t see the epoxy chemically breaking down over time. When fully cured, it becomes inert so I don’t see what’s left to break down. There are 100 foot sailboats all glued together with WEST SYSTEM® Epoxy that are 35 years old that are still in excellent shape. The largest wooden ship (over 200’ long) built with WEST SYSTEM Epoxy was rated by Lloyd’s of London as a 50 to 100 year ship.
Stated shelf life on our resins is three years minimum from date of manufacture and two years on the hardeners. For most end uses though, the usable shelf life is much longer. As an example, most of my WEST SYSTEM Epoxy at home is over six years old and it works for everything I need it for. Some customers have used 15 year old epoxy for non-critical glue ups and have been happy with the results.
Lastly, many high end knife builders have discovered G/flex Epoxy. Some claim it is the best adhesive for gluing handles that they have used to date. It provides the best adhesion to metals and dense hard woods of all our resin/hardener combinations.
Best regards,
Thomas Pawlak | Technical Service
Gougeon Brothers, Inc.

PRO-SET |888-377-6738
WEST SYSTEM | 866-937-8797

I responded to that email with a request for industry links spec'ing epoxy chemical bond life because it has been stated that West Marine spec's their epoxy with minimum 30 yr bond life. That response:

I’m wondering if he was quoting West System Inc., where we said something about 30 year service life related to our laminated wind turbine blades. He may have been referring to an article or a brochure that we produced years ago where we said our wind turbine blades were designed and built to last at least 30 years of service in a high fatigue environment. We actually ran hundreds of fatigue tests (compression and tension tests) our wind turbine blade laminate to determine the fatigue life. These tests involved hundreds of thousands of cycles per test and in some cases millions of cycles per test to see how long the wood and epoxy would hold up to the abuse. These blades were made with many layers of 1/10” thick Douglas fir veneer glued together with WEST SYSTEM® 105 Resin and 206 Slow Hardener. The tests validated that the laminate would last the anticipated fatigue cycles of the blades over their 30 year service life in the field. In the field, we discovered that the wood epoxy laminate was better at holding up to fatigue than the metal parts that the blades were attached to.
This type of “bond life” (eventual fatigue failure) is different than when an adhesive is used to hold adherents together that are not under significant load for much of the time- such as when used to glue knife handles to steel shanks. In this case, I would expect the epoxy strength to be fully available decades later because there are relatively few times that the glue joint was under load over the life of the knife. In other words, fatigue life does not pertain in this case because loads on the joint are quite low and infrequent.
I hope this information is helpful. I can’t think of anywhere on our website where we make a statement about “bond life” for joints glued together with our epoxy. I may offer to write an article on the topic in a future issue of EPOXYWORKS. You can check out the newsletter at:http://www.epoxyworks.com/.
With best regards,
Thomas Pawlak | Technical Service
Gougeon Brothers, Inc.

PRO-SET | 888-377-6738
WEST SYSTEM | 866-937-8797

Please understand I am NOT trying to bash anyone personally, but do feel there needs to be open discussion about epoxy life from the epoxy experts - not me, but the folks who actually develop the stuff. The emails from Tom are posted by permission. If anyone can post links to epoxy manuf's who spec their epoxy bond life I would really appreciate the links, either via PM, or preferably right here in open discussion. My biggest goal is to find "correct' answer - not necessarily "my" answer.

Ken H>

Thanks Ken for taking the time and effort to contact manufacturers and for providing their responses. I have been pondering the expected failure lifetime of the epoxied we commonly use.

Understand Brandon - those folks are talking about "real" epoxies. While some of the "big box" epoxy packages are good epoxy, I'm sure some are not so good and I wouldn't use them at all. I'd stay with name brand, tested epoxies that I knew were good epoxy. As Boss said before, it's more about surface prep than type of epoxy, as long as it's a good epoxy.

Ken H>

FWIW, my favorite is Industrial Formulators G2. I first bought it because it's "niche" is oily or waxy substrates and I was using cocobolo. It served very well on those knives and on many more since, including the restaurant steak knives I have referenced in other posts. Looooong cure.

DBAR said:

I've been using 30 minute slow cure from Midwest Knifemakers Supply. It's what was recommended to me a while back, and for the most part, it's worked pretty good.

I do a lot of segmented scales, and the 30 min stuff gives me plenty of time to get things where they should be before it's too late. I was reading on Insta Gram tonight, and someone made mention of some 30 second aircraft glue, made for work on airliners. It got me thinking. The 30 second stuff would be fast enough for me to get segments done individually and then glue them all together. Sometime the 30 min stuff takes too long, and things are still moving under pressure of the vices. That makes for some scraps, and a lot of time wasted.

Anyone use this 30 second stuff? Either way, I'd love to here some of your experiences with different epoxies.

Suggestions are welcome.



Thanks,

Don

Click to expand...

Don, I only use the West Marine G/Flex Epoxy after using many over the years from Devcon to Gorilla Glue.

One of the most important factor's is your preparation! I now leave my tang & handle scales at 120 grit and hand ruff my kydex liners with sandpaper to 120 G before assembly. I believe the use & fact sheet that comes with G/Flex says 80 grit. For a larger structural bond I can see that and I've been fine with 120 g so far. Along with a low grit finish I wash off all of the knife tang, scales & liners with Windex and place them on clean paper towels just prior to mixing up the epoxy so I have removed any oils and dirt from my skin etc.

Stay safe & have Fun!

Thanks everyone,

and thanks Laurence,

I've been doing the prep part right, except for I haven't been using a rough enough grit. I've been finishing the whole flat of my knives at one time. Meaning I finish the tang, and the blade flats up to 400, sometimes 600 grit. Then I'd rough up the tang area with the 220 before cleaning the scales and tang with windex, and then acetone. I guess I'd better start using some of the rougher grits I've got laying around. I have also been drilling additional holes through my tangs, and counter sinking the holes. I was doing this to allow the epoxy to flow through the holes and settle in on both sides of the tang. In addition I've been drilling dimples on the opposing sides of the scales. Lining the dimples up with the holes in the tang, letting the epoxy form "epoxy pins" so to speak.

I'm still trying to find the best epoxy for me and my style of knife making. I appreciate everyone's input, and I'll look into them all. I'm looking for an epoxy that will work best for me working with the segmented handle scale glue ups. If the epoxy is too fast, (5 min) I can't get everything lined up, and pressed in time. If it's too slow, I have some segments moving under pressure while the initial cure is taking place. This creates voids, or gaps filled with epoxy that will not be acceptable.


Thanks again,

Don

I use West Systems G-flex. I haven't ever contacted any epoxy company and talked to anyone but I will say this.

I have two knives from when I first started making knives. Which is about 5 years ago. Both are hidden tangs. Both of them were finished the same as far as surface prep. My surface prep has stayed constant over the last 5 years. One knife was made with G-flex and one was made with Devcon 2 ton epoxy (30 min cure time) from home depot.

Both knives were test pieces, (not testing epoxy, this is just coincidence) not meaning to be sold so I used them around home and camp. Both were fine for a long time (2 years or so). I pulled the knives out about 3 months ago or so to do something and the knife with Devcon epoxy rattles around and twists in the handle. Quite badly actually. So something in there has moved/shrunk/broke down.......something. The other knife is still as solid as the day it was made and I have literally beat the snot out of that knife, doing things sometimes you should never do with a knife.

Like I said, it was never meant to be a test of the two epoxies. By pure chance, between the making of those two knives, I just happened to switch and give G-flex a try due to all the good things I had heard about it on the forums. You can draw whatever conclusion you want from that. I know the conclusion I drew, with all else being as equal as I could make it concerning assembly and surface prep.

Don, there is some Loc Tite brand stuff that you wipe on then spray with a second part accelerator to cure. Supposed to be insanely strong. It's reported to be in instant set but someone I know who has years of experience with it says you do have time (about 5 minutes) before it's fully cured. I've never used it personally so I don't know.

I'm also thinking about how you make handles from what I've seen, and I used to make some the same way. I know the shifting problems you speak of as the epoxy cures over time. There are a couple changes you could make to your process that might help, if you wanted to.

1. you could use a couple hidden alignment pins to keep everything right where it should be.

2. you could assemble your pieces and superglue them to a g-10 liner first and then treat the scale as one solid piece. I've used Gorilla brand super glue for lots of stuff and have become so impressed with it that I have glued some very small scales on some small full tang knives a couple times. So far, no issues. I wouldn't trust other brands of superglue but the Gorilla brand is far superior to any I've used in the past.

Just some thoughts.

Acra-Glass from Brownell's #1................G-Flex from West Labs #2. There is no need to look past these two

I have used Devcon 2 TON slow set for thirty years. I've never had a come back for loose grip problems. I have a bone slabbed knife I made in the late nineties which was lost in a flood in 2008, recovered from wet mud 4 months later, and still seems as sound today as it ever was. I am not convinced at all on this short life of Devcon, nor that it isn't reasonably water proof or water resistant. I can only go by my experience with it, and that it has treated me very well. Could be that there are other over looked factors involved, but I like the Devcon.

I've used the Devcon 2 ton slow set for 25 years also, I have a couple of my first knives here at my shop and had many of my knives go on African safari's and used on a lot of big game there. I've also sold a lot to wild hog hunters here in florida, and the hog hunters I know,including myself are pretty demanding of their knives and in 25 years I've had ' 0 ' knives come back with any issues. I have noticed probably like everyone else here that if it isn't mixed at the right proportions it may not cure at the stated rate of 12 hours or so. here in florida I think humidity plays a big part of curing, at least what's exposed from the squeeze out. and of course cleaning the parts of oil and other stuff I think is THE biggest part besides proper mixing.
Having said all that about my results with Devcon, I do have a West Marine store half a mile from where I live so next time I need epoxy I'm going to get some G-flex and see if I like it better.
As for engineers be able to predict when their epoxy will break down...I don't know about that. I know my Dodge ram dash board started cracking about the same time millions of others did and everything seems to be calculated to break down shortly after warrantee but I don't think these instances are predicted by the engineers that designed them.

Tried the rest, now use Gflex exclusively. It works. On pretty much everything. Love that stuff!

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I use the gflex 655k. Is the thicker stuff that comes in the toothpaste tubes. Haven't had any problems yet. I also just grabbed some blade bond to try. We'll see how that works.

All of my knives now are made with the handle secured mechanically- full tangs with Loveless bolts or (occasionally) with peened pins, through tangs threaded to the buttcap, and hidden tangs with peened pins, so the epoxy is mostly just a sealer/filler for me. In my earlier years of knifemaking, before I had the internet and access to more information, I often used five minute epoxy to hold hidden tang knives together with no pins. I have a small paring knife that is a simple hidden tang in a curly maple handle secured with Devcon 5 minute Epoxy that has been used and abused in our kitchen for about ten years with no signs of failure. I'm not advocating that method, I don't use it anymore myself, and I'm somewhat surprised that it's still holding up. I gave a few knives away back then to friends that used the same method, and none have yet failed to my knowledge. These days, I'm very confident in my mechanical/epoxy combination using 2 ton epoxy, although I'm interested in the West product going forward.

I use E120HP very happy with it .