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06-24-2021, 01:44 PM   #1
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Tamron 24/2.8 (01BB) distance scale window attach

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The Adaptall-2 Tamron 24/2.8 (01BB) is a high-quality and compact manual focus option for 24mm. That said, there is a common problem with the lens in that the plastic window over the distance scale has a tendency to pop off, leaving the lens with no focus/aperture index mark and no DOF scale. Below is my copy with its errant distance window.




I would really like to see it back into its place and while it is easy to find reference to the issue on the Web, it is more difficult to find verified suggestions for a suitable adhesive. What I know:
  • It was originally attached at the far ends only with something that turned gooey with age
  • The curve of the window is tighter than the curve of the lens body, making it behave as a spring when attached.
  • Cyanoacrylate is not an option (will etch the window and other stuff).
  • Epoxy is an option, but I am concerned about and cleanup.
  • Weldbond is mentioned in several places, but with no actual success stories to back the suggestion.

What say the good folk here? Has anyone had success doing this?


Steve

06-24-2021, 02:00 PM   #2
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I'd be tempted to use a thin, clear, double-sided adhesive tape... Small pieces strategically placed at the ends and midpoint, or one big piece covering the entire back surface of the plastic component, with the edges and "letterbox" trimmed away using an X-Acto knife before bonding.

Something intended for crafts and general use (and, hence, not so permanent you can't remove it later) might be worth trying:

https://www.amazon.co.uk/Sellotape-1447052-Double-Sided-Tape/dp/B006N8UDQ4

Last edited by BigMackCam; 06-24-2021 at 02:14 PM.
06-24-2021, 02:23 PM   #3
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I would probably try some standard 2 part fast set clear epoxy. First I would see about removing any original adhesive. Next I would give the contact areas on the window and lens barrel a good cleaning with some denatured alcohol using a q-tip. Then mix up a small amount of epoxy and apply sparingly with a toothpick to the lens barrel where the window would come in contact with it. Then just press and hold the windows in place for a few minutes (until the epoxy set) and you should be good. When you press the window down into place the adhesive will spread so by putting a little on over a fairly large area you should get great adhesion and no mess. Cleanup then is as simple as tossing the toothpick and paper you mixed the epoxy on into the trash.

I wouldn't want to use solvent based adhesives and never super glue (CA glue). Cyanoacrylate (CA glue or super glue) won't etch but it has a nasty habit of fuming and then fogging things the fumes get on so it looks like it etches but that is just the vapors condensing on a surface and setting up. I looked up weldbond (I've never used it before) and it may work but it like like it is like a water based polyurethane glue that dries clear, similar to some wood glues. So given that I would probably still go for the 2 part epoxy as a solution.

I haven't done this repair but have played around with fixing lots of stuff and there are lots of adhesive solutions available with various properties that I have used over the years.
06-24-2021, 02:33 PM   #4
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I would use a contact adhesive like PlioBond or Gorlilla Clear Grip. These don't normally react with most resins/plastics and if need be the parts separated again. The old adhesive getting gooey with age suggests a polyurethane/urethane based adhesive which contact adhesives are commonly based.

06-24-2021, 02:47 PM   #5
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For similar jobs on camera equipment in general I've used contact adhesive (specifically 'Evo-Stik') with no problems. Needs to set overnight, so no problem with repositioning if necessary, then use a couple of elastic bands to hold things together whilst the glue dries. Just follow the instructions, spread it very thin and allow to become tacky before putting the two pieces together.
I'd agree with the reservations about using cyanoacrylate adhesive in this circumstance, too much risk of fogging the window.
06-24-2021, 03:09 PM   #6
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QuoteOriginally posted by BigMackCam Quote
I'd be tempted to use a thin, clear, double-sided adhesive tape... Small pieces strategically placed at the ends and midpoint, or one big piece covering the entire back surface of the plastic component, with the edges and "letterbox" trimmed away using an X-Acto knife before bonding.

Something intended for crafts and general use (and, hence, not so permanent you can't remove it later) might be worth trying:

Sellotape Double Sided Tape, Strong Double Sided Tape for Everyday Use, Mounting, Arts & Crafts, Easy to Use Double Sided Sticky Tape with Solid Grip & Easy Peel, 25mmx33m: Amazon.co.uk: Office Products
Good idea! I figure that the original adhesive was applied as thin film on a release layer, so doublestick tape might be an option.


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06-24-2021, 03:12 PM   #7
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If you don't want to use superglue, I'd give the thin double-sided tape a try. Some pieces cut with an x-acto knife and skillfully placed ought to work quite well. If it doesn't, then move on to the more goopy and risky epoxy/cement options.

06-24-2021, 03:37 PM   #8
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QuoteOriginally posted by MossyRocks Quote
I would probably try some standard 2 part fast set clear epoxy. First I would see about removing any original adhesive. Next I would give the contact areas on the window and lens barrel a good cleaning with some denatured alcohol using a q-tip. Then mix up a small amount of epoxy and apply sparingly with a toothpick to the lens barrel where the window would come in contact with it. Then just press and hold the windows in place for a few minutes (until the epoxy set) and you should be good. When you press the window down into place the adhesive will spread so by putting a little on over a fairly large area you should get great adhesion and no mess. Cleanup then is as simple as tossing the toothpick and paper you mixed the epoxy on into the trash.
I removed the original adhesive some time ago and all surfaces are clean. The original adhesive was limited to the two ends with a little at the near/far margins, but not all the way around. There is a volume constraint in that the recess for the window is essentially the same as the window thickness. Although the window did not originally fit flush, the original adhesive still must have been a very thin film.

The main issue with epoxy is the aspect of no second chance.


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06-24-2021, 05:11 PM   #9
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QuoteOriginally posted by stevebrot Quote
The main issue with epoxy is the aspect of no second chance.
I think that would be the case with most adhesives, however since epoxy dries hard and with a smooth nonporous surface I would think that it would be possible to get it to separate by applying some sheer force to a corner. It isn't like CA where your only option would be use use some acetone to free it. Weldbond would likely be much the same as epoxy as far as no second chance but both offer a fair amount of open working time with the epoxy setting up faster (typically 5-10 minutes). Neither one is like CA which has that near instant bond that prevents adjustments. If you wanted to have something easier to undo there is always rubber cement but that is solvent based and you would still have to apply it sparingly so it doesn't get forced places you don't want it.
06-24-2021, 07:19 PM   #10
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QuoteOriginally posted by MossyRocks Quote
Weldbond would likely be much the same as epoxy as far as no second chance
Softens with moisture and produces no fumes...it is a strange substance (polyvinyl acetate homopolymer).

Edit: Near as I can tell, that means it is something similar to Elmer's glue.

As for using sheer force to break the epoxy bond, I am hesitant to use sheer force on a irreplaceable part less than 1mm thick.


Steve

Last edited by stevebrot; 06-24-2021 at 09:53 PM. Reason: More stuff
06-25-2021, 08:43 AM   #11
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QuoteOriginally posted by stevebrot Quote
Softens with moisture and produces no fumes...it is a strange substance (polyvinyl acetate homopolymer).

Edit: Near as I can tell, that means it is something similar to Elmer's glue.
Ok so it is different than the one weldbond I found info on where it was stated as being a polyurethane based adhesive which is a completely different animal. And yes polyvinyl acetate homopolymer is similar to Elmer's glue and most wood glues. Depending on what else has been added there is varying about of water resistance with Elmer's being basically water soluble and on the other end Titebond III basically being waterproof.
06-25-2021, 09:11 AM   #12
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QuoteOriginally posted by MossyRocks Quote
Ok so it is different than the one weldbond I found info on where it was stated as being a polyurethane based adhensive...
There seems to be some confusion on the camera forums where some have asserted that Weldbond is the same as Pliobond, but packaged for a different market. Since both are common with crafters, model railroad, and other hobbyists some confusion might be unavoidable.


Steve
07-14-2021, 12:35 PM - 2 Likes   #13
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Update!

Weldbond does not work! Will not adhere to the painted surface!


Steve
07-14-2021, 12:44 PM   #14
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double-sided tape, the thin kind

If you can get sort of a seal with any method, but don't think it is secure, you could then also cover the entire thing and extending the edges out onto the barrel with just clear shipping tape -- a window on top of a window.
07-14-2021, 01:09 PM   #15
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QuoteOriginally posted by stevebrot Quote
Update!

Weldbond does not work! Will not adhere to the painted surface!
Useful to know, Steve, for others who might attempt a similar repair.

My money's still on a good, clear, double-sided, adhesive tape - after, of course, a good clean of the surfaces (which I'm quite certain you performed in advance of your Weldbond attempt)...
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