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03-06-2012, 01:38 PM   #1
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S-M-C Takumar Disassemble Issue

Hello guys, a few months ago I've acquired a nice looking Spotmatic II with an also nice S-M-C Takumar 1:3.5 135mm attached to it. the problem is that the rear metal cover of the lens fell off (looks like it should be glued on) so if I mount it on the camera it might hit the mirror (or worse..). It will probably work fine without it but it would probably make it very prone to dust and such.
So my question is, how should I fix this? can anyone recommend a type of glue I should use?

Thanks.

p.s. for reference, here's a quick snap of the back of the lens with the metal cover beside it


03-06-2012, 02:24 PM   #2
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QuoteOriginally posted by Pablom Quote
Hello guys, a few months ago I've acquired a nice looking Spotmatic II with an also nice S-M-C Takumar 1:3.5 135mm attached to it. the problem is that the rear metal cover of the lens fell off (looks like it should be glued on) so if I mount it on the camera it might hit the mirror (or worse..). It will probably work fine without it but it would probably make it very prone to dust and such.
So my question is, how should I fix this? can anyone recommend a type of glue I should use?

Thanks.

p.s. for reference, here's a quick snap of the back of the lens with the metal cover beside it
It is missing a few screws, that hold it in place. Ideally you should look closely to see where they came from and replace them otherwise cement. Lack of this baffle will cause internal reflections off the shiny internal parts and spoil the image
03-06-2012, 02:59 PM   #3
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Thanks for your help but there are no screws or screw holes to be found.

might regular 'super glue' be adequate for this?
03-06-2012, 03:10 PM   #4
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QuoteOriginally posted by Pablom Quote
Thanks for your help but there are no screws or screw holes to be found.

might regular 'super glue' be adequate for this?
The screws were in the small notches you can see marks from the screw heads and locking adhesive. I caution against super glue because it releases vapors that can damage lenses and coatings

03-06-2012, 03:26 PM   #5
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CA (Super Glue) also tends wick into all sorts of places you don't want it and its longitivity in many scenerios is questionable.

I'm guessing that, if you really have to glue it, a very small amount of epoxy (longer setting - not 5min / 30min stuff) would be a better bet.
03-06-2012, 04:36 PM   #6
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Mine has no screws at all, and a close look at your picture shows it's exactly the same as the one I have in front of me on my desk. The two notches are for the aperture pin and the square tab.

I agree that it it was probably glued from the manufacturer, but what sort of glue ? I don't know, and I'm disinclined to pull the shroud off mine to try and find out.
Personally, I would look carefully and see if any remaining residue from the original glue is in place, then I would also try and carefully remove the old glue.

I would use a soft glue, a contact glue, that could be prized apart if the need arises. It's not structural, all it has to do is keep the shroud in place.
03-06-2012, 04:56 PM   #7
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The best glues would be a 2 part exothermic adhesive which is known not to release any gas during the cure. There are some 2 part silicones that are like this, not sure about epoxies.
03-06-2012, 05:33 PM   #8
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QuoteOriginally posted by Lowell Goudge Quote
The best glues would be a 2 part exothermic adhesive which is known not to release any gas during the cure. There are some 2 part silicones that are like this, not sure about epoxies.
Most epoxies do release gases as they cure, they are a poor choice when dealing with optics which have chemical coatings.


Last edited by Docrwm; 03-06-2012 at 06:34 PM.
03-06-2012, 05:37 PM   #9
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Would the original design have used a glue that could be prized apart to enable disassembly ? Without trying it, I'm not sure if the shroud would even need to come off.
I hate using the really strong superglues on a part that might need to come apart, but they're great for repairing broken components. I've had a bad experience using superglue on a lens when a tiny drop dripped onto the aperture mechanism and that was the end of that !

But there are some excellent glues and adhesives out there now, it's picking the right one ? I know that I wouldn't use Gorilla Glue for one, it's a foam based glue that expands and gets everywhere, I hate the stuff.
03-06-2012, 05:57 PM   #10
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QuoteOriginally posted by Docrwm Quote
Most epoxies do release gases as they cure, they are a poor choice when dealing with optics which have chrmical coatings.
I thought so. I like silicones but the one part type release acetic acid, and with all the different types of metal parts, this leads to corrosion. That is why I suggested a 2 part silicone.
03-07-2012, 02:50 AM   #11
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Hi, I faced similar issue when I got my SMC Tak50/4. The part (ring) came off due aging of the glue that holds the part to the lens.

Upon examining closely, I could see some glue marks on the lens part and the ring. I glued the ring using UHU glue(not sure if it is available in yr market). I dab some glue (very little) to the glue marks on the lens and ring (UHU glue works like contact glue, I let it dry a little before bonding the parts). I work with real care to make sure the glue do not touch the optic, I use a tooth pick to accomplish this.

Till date the lens works well and the ring stays intact. Not sure if it is the same for the Tak 135mm.
03-07-2012, 10:43 AM   #12
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Thanks for the help guys. Yes, as Lloydy mentioned, there are no screws at all holding the piece.


Thanks for the tip jon_tan, I did spot some residue that appeared to be glue (and some rust too :'( ). I'm not sure what kind of glue is UHU but you're saying it's like contact glue?
03-07-2012, 04:28 PM   #13
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QuoteOriginally posted by Pablom Quote
Thanks for the help guys. Yes, as Lloydy mentioned, there are no screws at all holding the piece.


Thanks for the tip jon_tan, I did spot some residue that appeared to be glue (and some rust too :'( ). I'm not sure what kind of glue is UHU but you're saying it's like contact glue?
Hi, UHU works like contact glue but it is transparent in color, used mainly for art & craft. I suppose contact glue will also do the job
03-07-2012, 08:43 PM   #14
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QuoteOriginally posted by Pablom Quote
I'm not sure what kind of glue is UHU
UHU - Wikipedia, the free encyclopedia
03-08-2012, 03:23 AM   #15
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QuoteOriginally posted by Pablom Quote
Hello guys, a few months ago I've acquired a nice looking Spotmatic II with an also nice S-M-C Takumar 1:3.5 135mm attached to it. the problem is that the rear metal cover of the lens fell off (looks like it should be glued on) so if I mount it on the camera it might hit the mirror (or worse..). It will probably work fine without it but it would probably make it very prone to dust and such.
So my question is, how should I fix this? can anyone recommend a type of glue I should use?

Thanks.

p.s. for reference, here's a quick snap of the back of the lens with the metal cover beside it
I had exactly that happen to a SMC Tak 200/4. I fixed the problem with Loctite - the grade intended for holding threaded fasteners firm, but so they can be disassembled. Just a few small dots.

See my other post at:
https://www.pentaxforums.com/forums/general-technical-troubleshooting/152972-...-function.html
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