Can you solder magnets?

do you think JB Weld is better than epoxy? Just what is it? 

I don’t know if I’d say that JB Weld is better than epoxy, it’s
different. It is a two part system, one part is an off-white color,
the other is black. When mixed they turn gray. It’s working time is
about an hour, with full cure in 24 hours. There is a new fast cure
version, but I don’t have much experience with it so I can’t speak to
it’s long-term strength and durability.

JB Weld hardens much harder than epoxy and doesn’t soften with age
as epoxy often will do. It is hard enough to work almost like metal,
it can be drilled and filed, even tapped with threads. Once cured it
is impervious to any chemical or solvent I’ve ever used, like
acetone, MEK, gasoline, etc. The military version is called Metalset,
and is the only adhesive and patching material approved for repairing
punctured rotor blades and structural honeycomb composite panels on
helicopters. The stuff is amazingly strong and durable.

I wouldn’t use it for some of the things I use epoxy for, like
gluing pearls or dopping stones, or when appearance is a factor, it
is a flat, dark gray color when cured. But there are some things it
can do that epoxy just will not. Like repairing silver candelabras,
silver hollowware, a cracked flexshaft motor housing, things like
that. Just don’t use it on anything you might need to take apart
later. It takes a lot of heat to make it release, and solvents like
Attack won’t phase it. Once it has cured, it’s not coming apart
without a fight.

Dave Phelps

I don't know if I'd say that JB Weld is better than epoxy, it's
different. 

Yes, but not all that much. It is a steel filled epoxy. The steel
powder mixed with it changes it’s apparent hardness and reinforces
the end cured product, but the binder is still an epoxy resin.

That said, there are many varieties of epoxy, so the assumptions of
behavior and properties based on ordinary household epoxies cannot
be applied to all indiscriminately. Epoxies can be formulated for a
wide range of end result properties, including water or solvent
resistance, hardness, even temperature resistance (to a degree).
They are still epoxies underneath it all, just as rebar reinforced,
pre-stressed concrete cast I-beams are quite different from plain
old concrete poured for a sidewalk. But both are still concrete. And
JB weld is still an epoxy…

Peter Rowe

I mistakenly picked up the fast JB Weld once. ERROR !!! “Weld” cme
apart with very little provocation. Never touched it since. Regular
JB Weld is a wonderful thing. Around the house I wouldn’t be without
it. I would think a dab of it behind a grey magnet would be fine.

Justine

JB weld is still an epoxy... 

Peter, your concrete analogy was good one. But I’m wondering whether
the extra hardness of steel-filled JB Weld would have any benefits
in glueing a magnet or a stone in place, rather than a simpler and
perhaps more flexible basic epoxy?

Allan

your concrete analogy was good one. But I'm wondering whether the
extra hardness of steel-filled JB Weld would have any benefits in
glueing a magnet or a stone in place, rather than a simpler and
perhaps more flexible basic epoxy? 

Part of the problem in answering your question is that saying “basic
epoxy” is like saying “basic rock” there are hundreds of epoxy’s
each with different properties. Some are strong enough to be used in
assembling jet aircraft and others that are relatively fragile but
have other properties that make them useful. A good rule of thumb
for the retail variety is the longer the cure time the tougher they
are. Mixing properly and curing temperature can greatly effect the
properties as well.

James Binnion
James Binnion Metal Arts

Peter, your concrete analogy was good one. But I'm wondering
whether the extra hardness of steel-filled JB Weld would have any
benefits in glueing a magnet or a stone in place, rather than a
simpler and perhaps more flexible basic epoxy? 

I don’t really know for sure. My guess is that more depends on the
exact formulation of the epoxy binder than on the filler for this
application. The filler would be great for things where surface
durability of the material is in question, or for compressive
strength perhaps. But for simple bonding, like a magnet into a
properly fitted depression, my guess is that the flexibility, and
thus shock resistance, of conventional epoxies might be an
advantage. That’s my intuition, but I’ve no actual research data or
the like to support it. Best bet, of course, would be to try a sample
joint with each type, and subject it to the sort of wear or forces it
will have to hold up under. See for yourself which seems to work
better.

Peter

saying "basic epoxy" is like saying "basic rock" there are
hundreds of epoxy's each with different properties. Some are strong
enough to be used in assembling jet aircraft 

Yep. “Fiberglass Resin” is actually epoxy that meant for fiberglass
applications - the fiberglass is the cloth. And was it Peter who
said the old thing about “the longer the cure the stronger the
bond”? which is true as far as I know.

I don’t actually know if the steel in JB Weld adds any real strength,
but I tend to doubt it in any significant way. Mostly what it does is
turn runny glue into putty. We used to back turquoise with Devcon -
essentially the same thing as JB Weld, and we could lay out a layer
of 14" thick on waxed paper. And that’s the main advantage to JB, too

  • the ability to build it up…
I don't actually know if the steel in JB Weld adds any real
strength, but I tend to doubt it in any significant way. 

Oh yes it greatly increases its compressive strength over plain
resin but has little effect on the bond (shear strength).

James Binnion
James Binnion Metal Arts

What is commonly called fiberglass resin is a polyester not an
epoxy. It is a different beast.

Epoxy resins are more expensive and along with some others are also
used for rigidizing more specialized composites. Know your materials.

jesse