I was looking for the strongest epoxy this morning and none of the reference my favorite PC-7. I'll post a link below. Anyway I have on hand some PC-7, JB weld, and West System 205. Are there any others that you like that I might be able to buy locally. I'm thinking of gluing some steel rod to flat plates and then rig up a breaking test of some sort to see if i can tell the difference. I don't think I'll have any scales that might work but can probably clamp a metal pipe to the steel rod and then slide weights out the pipe to see how far or how much weight I can add before it breaks. Any other ideas. I did this with wood glues on butt joints with wood and it was an eye opener.
Do the surfaces being epoxied together make a difference. For example cement blocks, wood blocks, steel blocks or combination all have different porous textures so it seems holding strength using the same epoxy mix would be different.
Right now I'm looking at West 105/209 with 403 filler for a complicated glue up but haven't made a decision yet. I will need a long working time both for the number of pieces and my slow inexperience.
Re: OK I'm going to have to run an epoxy test *LINK*
Watched that video a few minutes ago. That's similar to how I did my test on wood glues many years ago.
Yes the materials being bonded together makes a huge difference. for this test I want to bond a metal rod to a flat metal plate. Somewhat similar to the robust tool rest although his rests have a concave groove for the rod to sit in. That would be too difficult for me to do on a short run like this and I think flat to round will tell me something. I may be going to town later today and will look at what's available. After watching the video I'm going to find some Loctite Steel to steel adhesive.
One thing I might do is to glue a bunch of dowels into some drilled holes to test for strength on my hand mirror handles. Trying to twist them out should tell me something. This will be a cross grain joint. Maybe I can glue 2 blocks together with a dowel inbetween with about 1/2" gap. Then when I try to twist the blocks it will either fail at one of the glue joints or the dowel will twist apart. If I just try to put vice grips on the dowel I'm pretty sure it will fail at the vice grip area because I've had that happen before.
Re: OK I'm going to have to run an epoxy test *LINK*
Re: OK I'm going to have to run an epoxy test *LINK*
Keith Newton
I'm not sure what you are trying exactly, or why you want the gray, unless you it's metal to metal, then you'd probably get a lot stronger with welding or brazing.
Here is a link to my favorite brand of epoxy. I've probably used over 100 gallons of this, after starting with West, and System 3. I really don't think there is a lot of difference in the epoxies, so much as the additives. For general woodworking, I keep colloidal silica to thicken however thick it needs to be for the situation, then add other stuff like dust from my belt sander bag for color.
The silica is extremely light weight, so when it is added the viscous cream/ paste will stay where I put it, rather than slowly sag and run out of a joint, due to the slow setting time. But there are many other additives that you can get to mix in for whatever properties you want to achieve.
You can probably pay twice that for some brands, but ask yourself, are you getting a product twice as good, or are you paying their advertising expense for them?
Take a look at uses for West System 404 High-Density filler. If you call them, they'll probably give you their smartest recommendation.
I just used a bunch of their G-Flex T Thickened Epoxy, which has a fairly slow set time and is easy to use -- press equal amount out of the two tubes, mix, etc. The instruction sheet with it mentioned sandblasting metal and also sanding it with wet epoxy as lubricant to get right at truly fresh metal.
Re: OK I'm going to have to run an epoxy test *LINK*
I want to play with the G-flex but may not have time to get some. We start all the running around to take care of my Stepson's Radiation treatments on Wednesday so I will possibly have no time to play after that.
Re: OK I'm going to have to run an epoxy test *LINK*
I watched that video and would like to offer a few comments as an engineer. Joints like this can fail in four main ways: adhesion failure, compression failure, tension failure and shearing failure. Often combinations of these occur, but one usually starts the failure process. In the video, the principal stresses on the joint obviously are compression at the bottom edge of the bolt and tension at the upper edge of the bolt. This is the consequence of applying the weight at the end of the bolt whose length is much longer than the diameter of the bolt head. Compression failure is not a likely problem here, because it would only result in the bottom the bolt head moving inward by a trivial amount before resting against the steel support. This leaves tension and adhesion as the likely suspects. Looking at the pictures of the failed bolt heads I see that each has a flat-sided blob of epoxy still attached to it, indicating that it pulled loose from the support rather being fractured. That being the case, differences in the size of the blobs of epoxy applied in each test case may have been more of a factor in the results than the characteristics of the epoxy. A further point is that these tests do not provide any useful indication of the shear strengths of the various epoxies. Depending on your application, this may be the most important factor.
