Bonding: Epoxy, adhesive of choice?

Andreas Thaler

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I'm just getting into the subject of bonding and am trying to classify the adhesives I already have according to their area of application.

So far for camera repair purposes I have experience with the following adhesives:
  • UHU extra for low-load connections,
  • Loctite universal and for plastics for permanent connections with medium load,
  • Pliobond for attaching leatherettes and everything that should be removable,
  • and now, for the first time, Epoxy.
I get along well with the first mentioned, I've only used Epoxy once. I'm impressed by the strength and the setting of the latter within minutes.




Nikon F-301: Fixing a spring with Epoxy


Can epoxy be considered the adhesive of choice for all connections that need to be as strong as possible and resistant to force from all directions?
 
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Dan Daniel

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Andreas Thaler said:
Can epoxy be considered the adhesive of choice for all connections that need to be as strong as possible and resistant to force from all directions?
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Simply put, no.

E.g., your drop on metal above: two modes of failure. One, the spring wiggles back and forth in operation. This movement extends up to the epoxy. This motion will slowly wear away the epoxy at the interface, allowing for more and more movement, more wear, expansion inward of the range of motion. Until eventually the epoxy is worn away enough for the spring to come undone.

Two, the attachment to the metal. Good chance that this isn't permanent and with enough sideways force it will fail.

Now maybe my possible failure methods are moot in your case because the wear rate of the epoxy will so much slower than the failure time for other parts of the system?

I think of epoxy as a reinforcement of a mechanical connection. So for example your spring- make slot or hole for the spring to seat in. Or thread a screw into the metal lever and attach the spring with this. At the least, provide a mechanical attachment for the epoxy itself- roughen the surface, make holes and divots for the epoxy to form itself into pins and such, etc.

Now there are a variety of epoxies out there. I had a broken camera part and someone who had experience with aircraft assembly suggested an epoxy. It worked well on its own but kept failing in operation becasue of sideways forces. I asked him about it and he apologized, that he didn't understand how small the part was, and that there was no way that his recommended epoxy would handle that situation- too little surface area and too much sideways force.

I know that there are much better terms for what I am saying and maybe someone will use them. And there are varieties of epoxies I have no knowledge of that might handle your spring. I'll be interested what one of the engineering-types has to say.
 
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Andreas Thaler

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Thanks, Dan!

The spring was previously sealed with red varnish, so I thought epoxy would be at least as good. The remains of the varnish are still visible in the picture.
 

koraks

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Dan Daniel said:
Simply put, no.
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Indeed. There's no silver bullet glue. It all depends on the materials to be joined, how well they fit together, size of the contact surface, the kind/directin and strength of forces the bond will be subjected to, environmental conditions the bond needs to withstand, possible limitations in the process (e.g. required speed of setting/hardening, offgassing affecting on nearby components), etc. etc. etc.

Then there's the issue of 'epoxy' being an ill-defined term; there are many types of epoxy, and moreover, 'epoxy' is often used as a generic term to identify two-component adhesives, which are not all epoxies in reality.
 
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Andreas Thaler

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koraks said:
Then there's the issue of 'epoxy' being an ill-defined term; there are many types of epoxy, and moreover, 'epoxy' is often used as a generic term to identify two-component adhesives, which are not all epoxies in reality.
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This post of yours also confuses me, as does your recommendation to always remove flux, even if it is specifically intended for electronic soldering with a code

My epoxy should be real?
 

koraks

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I didn't suggest your epoxy isn't "real". I pointed out that adhesives that are called "epoxy" aren't always that, and that not all two component adhesives are by definition epoxy. Moreover, there are many grades/types of epoxy. This was in reponse to:
Andreas Thaler said:
Can epoxy be considered the adhesive of choice for all connections that need to be as strong as possible and resistant to force from all directions?
Click to expand...

You need to differentiate, I think.

Having said that, "epoxy" as such is a fine adhesive suitable for many purposes. I often use it, but it also has its limitations. You'll find out, I'm sure. Sometimes it just won't adhere to certain kinds of surfaces and it'll just spall off cleanly.
 
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Andreas Thaler

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In relation to my application example with picture, I wonder whether the original red varnish was intended to be used as a fixation or as a sealant, for whatever reason.

If it was applied for the first case, then the next question is whether my epoxy drop is at least an equivalent replacement.

All I can do is test it myself.
 

koraks

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Andreas Thaler said:
If it was applied for the first case, then the next question is whether my epoxy drop is at least an equivalent replacement.
Click to expand...

In the second case also. To me, it looks like it was there to fix the spring in place especially in the face of mechanical shocks to the camera body (dropping etc.) causing it to be dislodged. No major forces are expected to be exerted on the bond and if (that's a big one, though) the epoxy has bonded well with the metal surface, I'm sure it'll do fine as it is.
 

Dan Daniel

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If varnish was used, most likely the spring has minimal movement and/or force and low risk of moving out of place. So very likely that a standard off-the-shelf epoxy will do just fine.

Now another thing to think about before you start using epoxy all over cameras: what about future repairs? Can it be undone if need be? Will it need to be undone? Like loctite- using loctite that requires 400F degrees to undo on a camera side panel is a mistake, I would say.
 

BrianShaw

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All good comments that are consistent with my use of epoxies over the years

I have questions, though.

Having never seen a spring secured that way, are you sure that’s a factory procedure or something else?

Also, if red varnish was previously used then why not red varnish again? It’s not like nail varnish is an obsolete material that requires a substitute
 
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runswithsizzers

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But what is the best adhesive to attach angels to the head of a pin? ;-)

Generally speaking, I have found various epoxies, with or without fillers, to be excellent for many kinds of repairs. I doubt you will find any class of adhesives better for joining dissimilar materials which are not a close fit. Within the class of epoxies, there is a lot of variation in specific properties, so it is necessary to pick one suitable for your specific repair.

Limitations of epoxy include:
- Epoxy will not stick to some kinds of plastics
- Very smooth surfaces may need to be roughened
- All surfaces must be clean and free from oil, wax, and grease (true for all adhesives)
- Working time may be inconveniently long or short depending on the formulation and temperature
- Some epoxies can start to weaken as low as as 140*F / 60*C; but there are heat resistant epoxies that can withstand much higher temperatures, 450*F / 230*C
- Epoxy may be too "permanent" in situations where subsequent disassembly is expected
- Degraded by UV light. Epoxy exposed to sunlight for prolonged periods should be protected by paint or UV blocking varnish
- Some people may become sensitized to epoxy, resulting in dermatitis
 
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runswithsizzers

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I guess I should mention some of the advantages of epoxy, as well:
- Gap filling (does not require close fit for strength)
- Waterproof (although there are a few formulations that may not be suitable for constant immersion)
- When cured, resists most solvents
- Electrically non-conductive
- Stiffnes, hardness, and tensile strength can be modified with various additives
- Can be molded, drilled, sanded, etc. so could be used to make plastic parts like film advance lever tips (hint: add black pigment powder to make epoxy black)
 
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Andreas Thaler

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I use what I have and what works. Of course, I can't meet the factory standards.

The spring is supposed to be fixed at one end, and that is met.

Likewise, I don't have the range of lubricants that Nikon specifies for the F-301 or other cameras and lenses, as those things are not (longer) available.
 
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Andreas Thaler

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Very helpful, thank you!
 
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Andreas Thaler

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Good point
 

BrianShaw

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Andreas Thaler said:
I use what I have and what works. Of course, I can't meet the factory standards.
Click to expand...

You really should add a bottle of nail polish to your arsenal of tools. It is ey to procure and a very commonly used technique to keep screws and parts secured. Epoxy, while perhaps what you currently have on your bench, is a bit overkill in that application.
 
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Andreas Thaler

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But then I would have to think about what color it should be and I would fail to buy it because I don't know my way around drugstores. So I'm going to ask my wife to get it for me

Thanks for the tip.
 

BrianShaw

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Andreas Thaler said:
But then I would have to think about what color it should be and I would fail to buy it because I don't know my way around drugstores. So I'm going to ask my wife to get it for me

Thanks for the tip.
Click to expand...

I completely understand. When I asked my wife to buy some red nail polish for me (different wife yet similar circumstances and application as you) she kept asking "which color red?" I should have asked for clear, perhaps.

What camera is that?
 
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bernard_L

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I'm more positive about epoxy. See my post: https://www.photrio.com/forum/threa...tiful-diy-repair-projects.204935/post-2773211
The epoxy I used was Loctite EA3450. I believe it is not available on the shelves of the DIY store. I selected it because it is well specified for metal-metal bonding, including shear strength. Best strength is obtained on grit blasted metals; I suppose that rubbing with fine abrasive paper may be a substitute.
 
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Andreas Thaler

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4season

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Plastic Cameras
I use:

JB Weld, particularly for cracked plastic parts, like the outer covers of my Bronica ETRSi and Jenaflex. Can be carved when partially set, and very useful for filling gaps.

https://www.jbweld.com/product/j-b-weld-twin-tube

Cemedine Super-X for attaching shutter curtains, ribbons, leatherette and many other applications where flexibility is useful. When cured, it has excellent adhesion and has a firm, rubbery consistency, but can easy be removed with naptha. Although it's not clear, I also like it for attaching glass and plastic windows because it doesn't seem to dry out and become brittle over time.

https://www.cemedine.co.jp/global/en/technology/elastic/superx/index.html
 

Individual One

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I have a quite a lot of experience in optical assembly. One adhesive trick from my past that may be useful here is something that is sometimes done for gluing optical elements into metal tubes where heat and vibration may be an issue. After an optic was positioned we would inject a material into the space around the optic (two component, but I don't want to name it to avoid giving away a trade secret) that would form a mechanically compliant bond that could cope with the thermal expansion difference between glass and titanium.
Another useful technique can be to modify the properties of off the shelf epoxies by the addition of a third component. To cope with thermal stresses one can add a filler to conventional two component epoxies to yield properties intermediate between glass and the substrate the glass is being attached to.
 
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