JBWeld Cold Weld Epoxy - Poor Results

[Dave9]

I can think of 3 alternatives.

1) Nut tightened too much

2) Bad batch of epoxy (or not mixed well enough, you have plenty of time to mix longer with the slow set JBW).

3) Just too brittle for the application. JBWeld is one of the brittlest epoxies out there, while all clear types I've tried, are more flexible, still set up hard but have some plasticity.

 

[Mazomopar]

Looks like tensile strength doesn't always equate to adhesion. Maybe if the metal surface was roughed up or scored it would allow the weld to key in. Always used JB for providing more of a mass replacement, with adhesion being second concern myself. I concur other expoxies out there place adhesion over tensile strength. Man, some of those 3M body adhesives are unbelievable.

 

[JHZR2]

Did you clean and degrease the metal
Items? If they had light oil on them, or were too smooth, epoxy can have issues adhering.

 

[wrcsixeight]

Ideal= 50/50 parts a and b.

37/63 thoroughly mixed still hardens, but how much strength is lost?

I have a digital scale. When squeezing part a then part b equal.size blobs , the scale.revealed 60/40 when eyeballing volume.

Some.epoxy are 1 to 1 by weight and volume.
Some.might be 1:1 by volume but 100:97 by weight.
300 gram scale with 0.01 gram resolutionis under 12$.

Squeezing perfect 50/50 Blobs, by eye, is basically impossible.
So sayeth the digital scale.

53 /47 might just be fine.
46/54 might not be.

Eliminate the variables.

 

[George7941]

Did you clean and degrease the metal
Items? If they had light oil on them, or were too smooth, epoxy can have issues adhering.

I did wipe down the clips with IPA but it really would not have mattered because the clip is mainly retained through a mechanical lock ( the epoxy extruding through the holes and then hardening) rather than through adhesion. The clip could have been made out of Teflon and the extrusions will still lock the clip in place.

 

[George7941]

Ideal= 50/50 parts a and b.

37/63 thoroughly mixed still hardens, but how much strength is lost?

I have a digital scale. When squeezing part a then part b equal.size blobs , the scale.revealed 60/40 when eyeballing volume.

Some.epoxy are 1 to 1 by weight and volume.
Some.might be 1:1 by volume but 100:97 by weight.
300 gram scale with 0.01 gram resolutionis under 12$.

Squeezing perfect 50/50 Blobs, by eye, is basically impossible.
So sayeth the digital scale.

53 /47 might just be fine.
46/54 might not be.

Eliminate the variables.

That is about the only cause of the poor strength. Not only was I just eyeballing it but I was not even paying close attention, just a quick squeeze of both tubes.

 

[doitmyself]

Wrong part A/B proportion might be the cause. 24 hour wait time? To expand on an earlier question I asked: 1.) Did you just push the epoxy through the holes to leave mushroom type extrusions, or 2.) did you also spread the extruded epoxy to encapsulate the entire top/bottom sides? If just the mushroom style, maybe not strong enough? Since this formulation is quite runny, I imagine #2 was used.

We've about run out of ideas.

 

[slug_bug]

I'm curious. Did you spread the epoxy over the top of the bracket after pressing the bracket into place, or did you just rely on the expansion of the extrusion. The video that doitmyself posted at 4:40 instructs to smooth the epoxy over the bracket. Seems like that might be critical to the success.

 

[George7941]

Wrong part A/B proportion might be the cause. 24 hour wait time? To expand on an earlier question I asked: 1.) Did you just push the epoxy through the holes to leave mushroom type extrusions, or 2.) did you also spread the extruded epoxy to encapsulate the entire top/bottom sides? If just the mushroom style, maybe not strong enough? Since this formulation is quite runny, I imagine #2 was used.

We've about run out of ideas.

 

[George7941]

#1. Next time I will do it the #2 way. The mix was not thick enough in the beginning to hold the clips in place. I waited for a half hour till the epoxy started to thicken and then pushed the clips into the patches of epoxy I had applied to the marble in the beginning.

If enough downward force is applied to a clip and it separates from the marble, the failure location will be at the extrusions where they pass through the holes in the clip. That was my reasoning for not smoothing and spreading the epoxy over the bottom of the clips. But, on further thought, spreading the epoxy over ties the extrusions together and spreads the load over the extrusions more evenly, helping prevent a cascading failure where the extrusions fail one after another.

This was my first time with these clips and I got some epoxy on to the threaded shafts of the clips. This created some hassle when I finally mounted the nuts on to the shafts. Next time I will use masking tape on the shafts.

Time for some math. Each hole in the clips is just over 3/16 in dia, which makes the surface area of the hole pi x 3/32 x 3/32 = 0.0276 sq ins.
0.0276 x 5000 psi = 138 lbs. So each extruxion should support 138 lbs.

 

[chrlsful]

#3 & 10 above. Plus use the standard proceedure for these solid surface tops. Each trade has specific techniques, products and methods for end goals. It's not car mechanics...