Adhesive to bond a pair of machined flat surfaces

[Craig BrownParticipant @craigbrown60096]

I need to sandwich 2 pieces of 150mm x 40mm x 10mm material together, one is copper, the other aluminium. I would like a tight join so intend to machine both surfaces flat. Once together they will be machined together as one part and remain together as one component. I have JB weld and super glue, will either of these achieve what I need or do I need something else?
Many thanks

[Robert Atkinson 2Participant @robertatkinson2]

JB weld being iron filled would be the bettor of those two as it should help reduce electrolytic corrosion. Also a bit tougher (impact resistant) than standard “superglue”
Ideally I’d use a two part toughened acrylic.

Robert.

 

[Mark RandParticipant @markrand96270]

I’d go for Araldite, after etching the aluminium with caustic soda/NaOH.

[Nigel Graham 2Participant @nigelgraham2]

Would it be advisable to etch the copper as well?

The caustic soda will probably not do that, but will degrease the surface.

[Charles LamontParticipant @charleslamont71117]

Is this assembly likely to experience significant temperature variation?

[Michael GilliganParticipant @michaelgilligan61133]

I would agree with Robert regarding Acrylics

… but the range of available products is enormous.

Your first stop should probably be the Permabond website, and specifically this page:

https://www.permabond.com/products/structural-acrylic-selector-guide/

From my own quick look TA4202 looks like it might suit your purpose:

https://www.permabond.com/wp-content/uploads/2023/05/TA4202_TDS.pdf

MichaelG.

[not done it yetParticipant @notdoneityet]

At 20mm total thickness, I would rivet or bolt them together, but it would rather depend on how they are to be used – of which we know nothing.  By all means glue initially, if you must.

If a one-off, I might just use a smear of loctite if the surface finish and flatness were appropriate.  How the final item is expected to operate, would also be a consideration.  I find your enquiry to be lacking in detail, I’m afraid

[Speedy Builder5Participant @speedybuilder5]

One could re-invent the wheel, but a known effective solution to the problem is already out there. just look up “REDUX bonding”  on the net and your answer is there.

Bob

[Craig Brown]

On 1 October 2024 at 17:36 Craig Brown Said:

I would like a tight join

How tight? The problem with the more viscous 2 part adhesives like JB and Araldite (not sure about permabond) is they tend to be quite thick so you will end up with more on the surface so the joint will not close up as tightly as if it were done with a more liquid adhesive.

[not done it yetParticipant @notdoneityet]

the joint will not close up as tightly as if it were done with a more liquid adhesive.

It would if clamped.  Def not if just laid together.🙂

[Michael GilliganParticipant @michaelgilligan61133]

Good point, Jason

… The Permabond TA4202 has a Maximum gap-fill of 0.5mm and I saw no reference to a minimum thickness … so it looks promising.

Further browsing by Craig would be advisable though !

MichaelG.

[not done it yet]

On not done it yet Said:

the joint will not close up as tightly as if it were done with a more liquid adhesive.

It would if clamped.  Def not if just laid together.🙂

You have obviously not tried JB weld if a large flat joint.

Even just applying it will leave you with a far thicker film thickness.

[Robert Atkinson 2Participant @robertatkinson2]

Just to re-inforce for the OP:

Of the two options you have to hand, JB Weld and “superglue”, JB Weld is the best choice for this task.

Robert.

[bernard towersParticipant @bernardtowers37738]

warming the two parts might as this makes most two parters less viscous.

[Craig BrownParticipant @craigbrown60096]

Thanks for the replies. The parts are far from exotic, they are vice soft jaws so I suppose the only consideration would be the subsequent clamping. The aluminium only really being used as a spacer as I need a greater thickness of material than the 10mm copper I have in plentiful supply. I could use steel, or I even considered brass and a soldered joint but this seemed wasteful as the brass is not in such a plentiful supply.

They don’t even really “need” to be joined together as they will ultimately be screwed to a vice but I just thought it would make for a nicer finished product.

The only reason I stipulated a tight joint was for aesthetic reasons, especially if using a darker adhesive like JB weld. If JB weld were used would clamping the parts together result in all the adhesive squeezing out?

Thanks again

[FulmenParticipant @fulmen]

Considering the intended use I would go for something more flexible than super glue or JB weld.

[JasonBModerator @jasonb]

For that use a few Rivits like NDIY suggests would do it. I’ve stuff I rivited 40yrs ago and you still can’t see the joint between the three layers of metal or the rivits themselves.

I don’t think you would be able to expel all the JBW by clamping

[FulmenParticipant @fulmen]

+1 on the rivets.

[Michael GilliganParticipant @michaelgilligan61133]

Well … it’s been an interesting, but ultimately unnecessary discussion, methinks.

MichaelG.

[Craig BrownParticipant @craigbrown60096]

I grit blasted the surfaces to be mated and tried JB Weld, smearing on both faces and clamped together. The join is plenty tight enough and the aluminium was decked down to thickness by just holding the copper and the bond held without issue. So for my needs, this appears to have been a success

[Robert Atkinson 2Participant @robertatkinson2]

Looks good

[Russell EberhardtParticipant @russelleberhardt48058]

Interesting thread here discussing the composition of JB Weld (and Loctite Weld):

https://www.photomacrography.net/forum/viewtopic.php?t=27987

One thing is clear, the tube marked Steel doesn’t contain any steel.

Russell

[Michael GilliganParticipant @michaelgilligan61133]

Excellent link, thanks Russell

MichaelG.

[egaParticipant @ega]

On the question of how much adhesive remains in the joint, I recall that some adhesives have to be used with microscopic balls in the mix so as to act as spacers to maintain the necessary thickness of the adhesive film.

I think they were called ballotini.

[Author]

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