Epoxy de-bonding... yikes!

M

manicreader

Joined
Jan 2, 2003
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71
I've been on a handle making spree lately, and I use alot of Devcon 2-ton, 30 minute, two part epoxy (waterproof). I usually file/drill/gouge divits into both mating surfaces. I then mix a small amount of epoxy, apply the epoxy, clamp it, and leave it clamped for 18 to 24 hours.

So yesterday, I'm grinding stabilized wood that I had epoxied to a liner and suddenly it feels funny, so I check it out and the whole front section has lifted from the liner. A gentle twist, and the rest of it lifts right off! What epoxy is left clinging is kinda wet and gummy, but not sticky. There is actually a thin film of epoxy still there, and I find that I have to sand it off before I can start over.

I figure, 'maybe I got it too hot'. Maybe heat might make it let go.

But then today, I'm handling (not working) a different knife assembled with the same batch of epoxy, and this one did not have near the intensity of grind (IOW less heat), and the bolster falls off in my hand! I've been using this knife as EDC for almost 2 weeks with no problem!

Obviously, I have failed to learn some basic tenet of epoxy use. Someone please help me... what have I forgotten!?!?

P.S. these are all folding knives, and I have one other that I have EDC'd for several months from the same epoxy batch and it is still fine.
 
Did you wipe all surface's down with acetone first to degrees them?

Actually epoxy won't hold bolsterd and scales on very good by itself,you need pins to do the holding.It doesn't take much heat to break the bond either,I learned that the hard way years ago when learning and grinding longer than I should have at one time.The bolsters will heat up and thus follow the loners and heat the epoxy before the scales will and that could have been what happened to you on this one.
Bruce
 
Another thing that will make epoxy let go is vibration. I quit using it on everything but stick tang knives because of this.
 
It also won't setup properly below about 72 degrees F.
I've had Devcon 2 ton go bad from storing in the shop. Extreme heat, or cold can cause it to go south in the tube/bottle.

I store mine in the house year round, and during the winter, mix, apply, and let cure the epoxied items in the house too.
 
Solve your whole epoxy problem by using Brownell's Acra Glas. I use their jel. Yeah,fellas, I know, here I go again on the 'Glas!
 
manicreader...

Hi this is Daqo'tah, and I as well have had a few problems with the 2-ton epoxy in the past. I believe that most of the problems are caused in my case by my errors in its use.

I had a handle fail once when I placed the knife on the cement floor to allow the glue to dry. This kept the temp of the glue too low.

I had another handle fail when the inside wood parts of the handle were not cleaned.

I just also noticed a problem with a knife I finished last week. The bond between the brass guard and the spacer material failed. I have no idea why yet...

HOWEVER:::::

However I have also had to cut both wood and micarta handles off when something else went wrong and so i was able to look at the way the 2-ton epoxy came out. In both cases the joint between the steel of the knife tang and the handle material (wood or micarta) was very very good!

I always notch the tang of my sub-tang knives with the idea that the notches should hold the epoxy better, and this has proved to actually work. Both handles I have had to remove showed signs that the notching did help.

One more thing,,,I had one other handle fail a long time ago when I clamped the two handle scales to tightly...I had squeezed the glue out of the joint.
 
I think I have the clean surface problem sewn up, but the temperature angle looks promising. I keep the epoxy in the house and also use it indoors, so temp is always at least 68 deg, but I'll try a little higher.

This stuff seems to have no date code at all. It took me about 45 days to use all of the epoxy in this applicator, so I'm wondering if the 2 components can 'oxidize' or something.
 
It would take more than 45 days for the epoxy to go bad in the package. Here are some possible causes of your problem:

- the epoxy was kept too long after you bought it
- the epoxy was kept too long before you bought it
- the ratio of the two parts was incorrect by too much
- only one of the two parts was used :footinmou
- mixing surface or stir stick was not clean
- not all of the epoxy was thoroughly mixed
- mixing a second batch of epoxy using the same mixing surface as previous, unset batch
- disturbed joint before epoxy was set


Using a stir stick that is too soft often will lead to incomplete mixing. Scraps of cable ties work well for this. After applying the epoxy, put the stir stick back on the mixing surface and leave it next to your work area. When the stir stick is firmly stuck on your mixing surface, the epoxy in your handle should be set.

Hope this helps.

Phil
 
Use K&G 24hr epoxy since you are clamping it that long anyway. Clamping 30 min epoxy 24hrs won't make it work better:D
K&G has never failed same for Acra Glas the rest of it I might use just to hold a part in place temporarily. The cost is about the same and it works ten times better.

You also may be clamping it too hard!
 
Most of the epoxy problems were pretty much covered. One thing I can add is that all epoxy cures slow and requires a warm temperature no matter what the manufacturer claims.
A 5 minute epoxy only applies to the initial SET. The Cure is usually a week or more at temps over 68 degrees. (maximum strength could be a month or more if irregular temps factor in)
Even so called ,cold temp, epoxy cures slow.
I strongly advise taking all knives where epoxy is used in the house if your shop cools down at night for at least a week if possible.
I've researched this extensively and have suspended the use of epoxy for the boat I'm restoring until the spring, even though it's in a greenhouse type structure because I can only heat it in the day when I'm working there.
Of course you should evaluate the risk factor in deciding how much time and trouble is needed in the cure of your product but you should not overlook the slow cure factor all exoxies posess in making the decision.
 
Manic,

My $.02. (Pretty much what others have said.)

I use acraglas, and some 2 ton. Here's my 'requirements' for a good bond:

Clean: I use break cleaner and soap and water. If the water doesn't bead you're clean.

Mix the epoxy EXACTLY 50/50 - no option throw it out if you think it isn't right.

Stir for a long time. You have 30 minutes, so spend the first 5 stirring.

Smear/rub both surfaces - there isn't a wetting agent in there so you have to work it into the surfaces a bit.

Clamp

Pre-heat the oven to about 150 degrees and turn it off. Then place the knife in there and let it still over night.

It'll stick,

Steve
 
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