Testing for the ultimate adhesive

[SteveS]

tmickley and I love everyone here. But, there are different factions among us. "What?" you say. "How can that be?"

The difference is adhesives. We put our faith them. We trust them when the chips are down (or the pins are loose). And we follow our favorite blindly, never having the time and money to try the vast array that?s available.

So, Tracy and I have set out to dispel the myths. To end the dispute or maybe we just want to stir up the pot .

Tracy and I are testing a variety of adhesives (not all epoxies) to see, as best we can, which ones will hold up the best for standard knife construction.

Please note we?re not about to compare HOW to construct a knife. That?s a religion of a different color. We?re only setting out to see how certain adhesives perform under a variety of conditions. For example, one adhesive might have better shear strength or peel strength than another. But it?s thick and ugly and no one would use it on a knife. One might hold well at room temp, but fall apart in the snow.

Because we?re testing epoxies and not methods, we?re using blocks of whatever simply attached to steel ? no bolts, no peening, no hidden pins, just epoxy testing.

Tracy and I are also using different methods and tests and conditions. I believe this will help evaluate the results.

Given that, let the games begin! So, belly up to the bar and place your bets!

And may we all learn a new thing or two.

Steve

[SteveS]

So here are my contenders:



1. Loctite Xtreme
2. Loctite U-05FL Flexible Commercial Adhesive
3. DEVCON 2 Ton Epoxy
4. Loctite E-120HP
5. JB WELD
6. Acraglas Gel
7. West Systems Epoxy (10 min Pot life)

Process:

I 'glued' the samples to a single bar of ATS-34 hardened to 60HRC. The bar was roughed up with a new 80 grit belt. The bar was then scrubbed with Simple Green, then sprayed down with Brake Cleaner.

The samples are dymond wood abraded with a 36 grit disk.

The clamping was done with hand clamps - loose enough that the block could be slid underpressure fairly easily.

This was done on Tuesday, March 8th at 9PM. Curing started with a light bulb over the sample to keep it warm over night. It's been at room temps since then (68 to 80).


Steve

[SteveS]

Thursday, March 10th 10pm.

I ground the samples flush with the steel. By evaluating the glue lines I've found:

1. Loctite Xtreme:

It's a thick gel like stuff. Hard to get smooth coverage. It needs a good squeeze. But the glue line looks fine.

2. Loctite U-05FL Flexible Commercial Adhesive

This stuff is a urathane (sp?) adhesive and bubbles/expands while it cures. I've used it before and learned it requires heavy clamping to keep the glueline looking good. With light clamping the glue line doesn't look so hot.


3. DEVCON 2 Ton Epoxy

Glue line is fine, but under microscope there some tiny gaps on one side - and I mean tiny. Maybe I didn't apply it perfectly right there at the edge.

4. Loctite E-120HP

Looks fine.

5. JB WELD

Leaves a thicker glue line and is visible on one side. It's thinner than I thought it would be, but will probably always show something if used for handle slabs. It's visibly not the color of stainless steel.

6. Acraglas Gel

Looks fine.

7. West Systems Epoxy (10 min Pot life)

Looks fine.

Steve

[SteveS]

Oh Yeah, I forgot to note. In a previous round I tried silicon, a commercial super glue, and Gorilla glue. The only one that survived was Gorilla Glue. That stuff, I believe, would make a great adhesive for knife handles. However, as it expands it makes an icky, stick foam. If it expands onto the ricasso, I don't I'd ever get it cleaned up. And you'd have to watch for a long time as it hardens. Once that foam hardens you have to grind it off to remove it.

So, it's off my personal list of usable products. If you can deal with the mess, I'll bet it'll make a great glue.

Steve

[Chris Daigle]

Steve, in your photo you show a bottle of Gorilla Glue. Are you going to include it in your testing? I had always wondered about that stuff and their claims.

Chris

--------------------

EDIT: you just answered my question! Thanks.

[tmickley]

I have three kinds of polyurethane glue, including Gorilla glue, curing now. I'll start posting some pics and progress this weekend. Steve has done one round of testing already. He's on round two. I'm on round one. Chuck Bybee sent me some metal and wood to use for round two. Currently I have 15 kinds of adhesive curing now.
Here's a starter pic with part of the first batch:

[Ray Rogers]

I think this is a great test and look forward to the results. Thanks for doing this.

If you get the chance, try some of K&G Finishing's house brand of epoxy. I've heard some say it is similar to acraglass. It's ivory colored, quite thick when mixed, and incredibly strong. The only downside to it is that it must be mixed by weight rather than by volume....

[weko]

Hi guys,

this is one of the top threads I've ever read even if it has put me off using Devcon. I mostly make stick tang scandi type knives where I cannot always rely on any pins or bolts holding the tang. Therefore a very good slow curing adhesive is more than essential for me. I live in the UK and after I finished reading started to search for Acraglass and Loctite Hysol E120.
No success though. They only sell Acraglass Gel for gunstock and there's no sign of L. Hysol E120 to be sold in England.
Do you know if it is sold here or what's the trade name in Europe?
Would you suggest some equivalent for me,please.

Your help would be much appreciated.
Thanks a lot,

Pete

[chrisinbeav]

There is one adhesive I would like to try. It's made by a company called Fusor. Typically they make autobody adhesives not knife adhesives. There is a particular one that is for panel bonding. (panel bonding...the adhesion of outter non-structural or semi-structural parts body parts)
I figure if this adhesive is crash tested, which it is.... shouldn't it work on a knife? The only problem... it's kind of a pale green color when dried and it has micro beads in it. The beads ensure a layer of adhesive between two panels. It might be a bit too thick though for custom knife tollerances.

Chris Nilluka

[DaveL]

LocTite 330 is a very good glue for micarta handles but the shelf life is a problem sometime. It is one I would be curious about in the tests though

[SteveS]

Thanks for the updates and detailed information!

It's odd that my personal testing has moved away (temporarily) from the epoxies to the preparation methods. I've had failures that I don't think should have happened. I can't tap anything with a hammer like Tracy!

So what's the difference. The type and condition of the steel is one. Plus how the steel is cleaned prior to use.

I won't be suprised if we end up with something like steel. You know how we tell people, "Heattreating has more to do with performance than steel choice". Well I think we might end up with, "How you prepare the materials is more important than the epoxy choice" (Of course that's not the whole story, but it doesn't matter how good an epoxy you use is, if your steel is oily when you put it on.)

BTW In another test I found most epoxies shrink on curing. IF you have large gaps under your slabs, the epoxy will actually pull away from the steel as it cures! JB Weld, acraglas, we the only epoxies I tried that didn't. Gorilla glue and U-05fl both expand. Something to think about!

Steve

[tmickley]

One broken to failure piece, one not yet tested. Three of these were constructed using PC-7 epoxy (which is amazing stuff) to test what affect (or is that effect? I can never keep those two straight) surface preparation has on a joint quality. One set had no surface prep, one was sand blasted and another was roughed up using a fresh, sharp 36 grit belt.


Here you see the load test. I added 25lb bags of lead shot. Here is a picture at 50lbs where the metal is actually bending under the load and the joint is still holding strong. The size of this joint is maybe 1&1/2" square. I was really impressed with this PC-7 stuff. Maybe all the others would have held just as well. I may do a couple more tests to see but I was still impressed. All three held 75lbs, all three failed as I added another 25lb bag so I never was able to accurately measure, by weight, how much each surface held but we can still draw some valid conclusions I think.



The joint to the left is 36 grit, the middle sand blasted surfaces and to the right no surface prep at all. Starting from right note one piece ended up with most of the epoxy and the other piece had maybe 50% of the surface with epoxy residue. In all three cases, the epoxy failed, not the material, but in the test pair on the right, the adhesion partially failed by not sticking well to the metal. The left pair shows fairly even epoxy failure with 10% or so adhesion failure. The center test shows very even expoxy failure with no adhesion failure visible. The residue coverage was very even on both pieces. The conclusion we can draw is that sand blasting a surface is clearly the best method of surface preparation followed closely by a good, even ?scratched up? surface from a new, sharp 36 grit belt. I?ve been using a 36 grit belt but going forward I will be using the sand blaster to surface prep any where I can for better adhesion performance.

[McAhron]

A good way to check for residues is to take the simple green or any other cleaners and mix it according to the instructions and spray a piece of cleaned glass,wait for it to dry and look at it from an angle to see if there is residue.I have tried cleaning windows with simple green and i can tell you it leaves a residue that has to be be polished off with a dry cloth afterwards ,or if left on its own streaks your windows.Acetone isnt good for surface preperation either because it is common for the acetone to have some levels of varnish and other impurities such as kerosene.Alcohol if its the 99.99 stuff works very well but many of the ones sold are only around 70%.I would have to say i think your both right that the best preperation is newly abraded metal that hasnt even had time to oxidize.I realy appreciate folks like you two who take time out of their busy schedules to benifit all of us.Thank you and i look forward to the final results.

p.s no pine rosin?

[peregrine]

This info is great! Just a thought, after the tests are complete, I am now wondering how the holding power of silver solder would fair similarly (in your joint steel on steel tests), since "you are only as strong as your weakest link."
Just a thought.
Roger

[SteveS]

Tracy,

I was thinking about the forces in your last test. That PC-7 stuff is amazing!

Steve