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The Newbies Arena Are you new to knife making? Here is all the help you will need.

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  #1  
Old 10-22-2017, 03:30 PM
michos michos is offline
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High quality adhesive that can be sanded within 2 hours?

Ive been making knives for a while now and have always found it best to use a high grade epoxy that sets overnight to adhere the scales to the tang...however, I now need to find an adhesive that sets and can be sanded within two hours of application. Does such a thing exist? If so, any luck using it?
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  #2  
Old 10-22-2017, 04:43 PM
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What you're looking for is generally known a "5 Minute" epoxy. As with most things in Knifemaking, you will have "trade-offs" you will have to be willing to accept, in order the get the fast cure time.

Fast set epoxies are not waterproof, even though some might advertise it..... also, the faster the epoxy cures.....generally the weaker the bond. Also, be aware that the majority of commercially available epoxies have a 2-3 month shelf life, and a hold life of 5-7 years.

What that means is that in order to achieve the best bond, the components should be mixed/used within 2-3 months of production. The "hold life" means that AFTER the components are mixed AND cured, within 5-7 years the epoxy will start chemically breaking down. That doesn't mean that things will magically fall apart at that 5-7 year marks, it just means that when things begin to degrade.

I learned this the hard way..... I had made a number of knives with a common epoxy, and about 5 years later, I had a rash of knives returned because their handles were "loosening" on them. What happened was the epoxy had chemically broken down. After a lot of research, I spoke with a chemist as a major chemical company who's job was designing 2 part epoxy. Long story short, he told me that his job depended on selling epoxy, and he would never engineer an epoxy that would last forever..... and that almost all of the commonly available 2 part adhesives are designed to fail slowly at the 5-7 year mark after mixing/curing Some of those knives there were returned to me were 10+ years old. What I found when I removed the handles was that the epoxy had crazed (a bunch of fine cracks), and in some areas the epoxy had turned to a dry white powder.

After more research, I started using Brownells AccraGlas. It's a rifle bedding compound, in a 2 part format, but it is guaranteed to have a 10 year shelf life, and a 50 year hold life. I have used it ever since, and have never had another knife returned for "loose" handles. (that was over 20 years ago). Next in line for shelf and hold life is West System Marine epoxy..... 5 year shelf life, and 20 year hold life.

The drawback? Both are "long cure", meaning that you have to allow them to cure at least 24 hours before working on them, and 72 hours for a full cure. So your options are basically use an adhesive that will cure in the time you want, but likely will fall apart in a few years.....OR use an adhesive that takes 72 hours to cure, but will likely last a lifetime.

At some point in time someone MIGHT develop a fast curing epoxy with a long hold life, but currently there is no such thing on the market. You have to pick and choose what's the most important to you..... fast cure time, OR long hold life.


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Last edited by Ed Caffrey; 10-23-2017 at 09:20 AM.
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  #3  
Old 10-22-2017, 05:41 PM
damon damon is offline
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LOCTITE 324 with the 7075 activator. its not cheap, but I refer to it as "god commands the to stay glue"
sets fast and does not want to let go. you need to be ready though because your work life is not long at all.
spray activator on both contact surfaces. allow to dry. apply bead of adhesive and quickly clamp in place. by the time you get the 3rd one clamped, the first one will be set for the grinder.

other than this stuff.... as Ed mentioned... ACRAGLAS would be the way to go. but.... patience seems to be a "4 letter word" now days.
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Old 10-22-2017, 06:14 PM
jimmontg jimmontg is offline
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Ed does the 5 year hold time apply to the long set up epoxies as well? I have always used them and always used pins and screws too. I just sold a knife last year I made in the 90's and it was the overnight epoxy and it wasn't coming apart. I haven't had a knife come back because the epoxy came loose. I also use JB Weld and it glues to metal really well, I use it mostly for hidden tangs. I have also and still use some Cyanoacrylates CA glues if I need a quick bond, it's a Loc-Tite product too. This is the first time I have heard about the glue coming apart in 5 years.


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Old 10-22-2017, 09:45 PM
michos michos is offline
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Many thanks for the info Ed and Damon.

For the LOCTITE 324 with the 7075 activator - sets really quickly but also, think you can sand it down within two hours? Same question on the 5 minute epoxy. I made my first 5 - 10 knives with 5 min epoxy. Most of them still seem fine but I believe that the scales on at least one or two have started to separate a bit. Ive never tried sanding it that quickly though. You think it would also be sandable within 2 hours? Ill probably do a test on both.

Between the two, which do you think would have the longest hold life?
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  #6  
Old 10-23-2017, 08:18 AM
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Quote:
This is the first time I have heard about the glue coming apart in 5 years.
I'd never heard of it either..... until it happened to me. I've had a lot of folks chide me over saying what I do about epoxy chemically breaking down, and my response is to believe whatever they want..... I spent a lot of time and effort to discover the information, and since it came from a chemist who designed epoxy for a living, and based on my experiences, I believe it.

Concerning the particular epoxies it applies to.... I can only tell you that the individual I spoke with told me "All commonly available commercial epoxy is designed this way." He also told me to pay particular attention to an adhesive's "hold life" as indicated on the label. You can expect it to last at least that length of time. If a label does not list "hold life", then 5-7 years is the norm. Keep in mind that I never said things would fall apart in 5-7 years..... only that the epoxy is engineered to START chemically breaking down in that time frame. It could maintain it's bond well beyond that.
This is my full time, long term business, so I might have a different view than others....but once I send a knife out the door, the idea is to never see it again..... only because if I do, it means there's likely a problem/issue that requires my attention, and I obviously didn't do something the way it should have been done. Most never give any consideration to "epoxy", and just assume that it's "forever".....and so did I, until I had a problem.

I can tell you that when I first learned of this, I was flabbergasted, because in my mind epoxy was "forever"....but if you look at it from the business viewpoint of those who produce it, it's not far fetched at all.


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Last edited by Ed Caffrey; 10-23-2017 at 10:23 AM.
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  #7  
Old 10-23-2017, 12:20 PM
jimmontg jimmontg is offline
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The epoxy I have doesn't say a thing about hold time, but I don't doubt you Ed, I guess because I use pins and screws my knives haven't come apart. That knife I sold last year was over 20 years old and was cocobolo with an ironwood pommel (tapped and screwed on) and it was a 24 hour epoxy. I guess I'll switch to accraglas and thank God I didn't just use a couple of pins, but l tended to use smaller, but more numerous pins. I just like small pins. I even have 1/8" loveless screws.
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Old 10-23-2017, 12:58 PM
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Hey Jim!

I suspect that not everything that's put together with "standard" epoxy is going to literally fall apart at that 5-7 year point, but just knowing that it has built in obsolescence, along with having the situation occur to me, has made be very cautious about any adhesive. If I can keep one individual from having to go through the same experiences I have, then it's worth the time to type it all out.

The longer I build knives, the more and more I realize that there's trade offs in just about everything we use/do in the process. It's just a matter of learning what they are.
AcraGlas isn't without it's own quirks...... getting the mix ratio correct can be difficult at first (it's mixed 4 parts resin to 1 part hardener), but the mixing cups that Brownells sells makes it much easier. I've also never found anything that will "cut" (clean up) cured acraglas...... usually if you get it somewhere you don't want it, the only option after curing is to grinder or sand it off.

Between the time I had loose handles coming back to me, and settling on Acraglas, I made everything with some type of mechanical fastener..... I think it's just cheap insurance.


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Old 10-23-2017, 02:15 PM
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Ray Rogers Ray Rogers is offline
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I swear by AcraGlas as well and it was Ed's advice that pointed me in that direction. The easy way - and I'm lazy so the easy way is always my goal and better still if it is cheap - is to use veterinary syringes. You can get them in feed stores and probably in some of the larger pet shops or on eBay. They come in different sizes and you don't need to buy needles, just the syringe and they are cheap. Use one for the hardener and one for the epoxy part, its easy to measure 4:1 that way. After using them, suck up some Acetone with them and squirt it back out several times (its re-usable) and the syringes will last for a long time.....


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  #10  
Old 10-24-2017, 06:54 PM
michos michos is offline
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Great info guys. When I have the option, I will definitely use high quality, longer set epoxy as I generally do. But in this case, since it must cure within two hours so that I can continue on with shaping the handle the same day, which product do you think would work best? 5 minute epoxy or LOCTITE 324 with the 7075 activator? Do you think that both products would actually be sandable within two hours or will they likely gum up? I can do a test run with the 5 min epoxy because thats cheap but Id rather not spend $75 on the loctite unless it seems like its going to be my best option.
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