Lens thread adhesive

[jlpape]

Hello,
I have a 35mm V4 Summicron that every once in a while requires tightening of the lens assembly to the focusing helicoid. The lens unit is tightened by removing the lens mount then using a spanner to tighten a ring holding the lens unit in place. Not tightening the ring allow the lens unit, including the aperture ring and lens hood (rectangular) to rotate in relation to the helicoid and lens mount. I would like to apply something like Loctite to the threads to prevent loosening of the ring the next time I have to do this repair (not that often). I have read some posts where folks cautioned the use of certain adhesives due to their tendency to out gas and impact the optics.

Are there any specific adhesives that are used in lens assemblies that will allow disassembly as well as be safe for the optics? One post did say that Loctite will out gas, but I have not found literature that would support this statement.

Thank you.
Jim

 

[BrianVS]

Personally- I would not use an adhesive before trying some other solutions. If it is a retaining ring that screws into place to tighten the barrel down, I would try Teflon Tape as used for plumbing fixtures. I've done this before- it's worked for me.

 

[Sirius Glass]

A drop of the weakest Loctite, I think it is blue. Red is way too strong.

 

[shutterfinger]

Use a drop of Locktite 242 (Blue) thread locker about the size of a flat straight pin head. Clear fingernail polish, a trace about the brush width across the threads, will work as well and is similar to the sealant used in manufacture.
Any out gassing of either of these is minuscule.

 

[jlpape]

Thank you for the replies. Teflon definitely will not out gas and a small drop of Loctite or nail polish should minimize any effects (if any). Thanks again,

 

[AgX]

A drop of the weakest Loctite, I think it is blue. Red is way too strong.

I would not use Loctite at all, if you mean the cyanacrylate glues. For two reasons: the glue is hard, if at all, to break/to remove once disassembly is necessary and nasty vapours can occur (only in case too much glue is used that would not cure).
Instead a thread-locking glue may be considered. It can be broken by force and emmits no nasty vapour.

 

[rockpowered]

Many camera repair manuals recommend using lacquer to lock threads on internal adjusting screws. If it was standard practice in the past it should be fine now. I use nail polish myself. I also use only the most minimal amount which really controls any potential off gassing.

 

[mike c]

If using small amounts of thread locking stuff leaving the lens detached from the camera for a few days to a week should out gas it enough.

 

[shutterfinger]

I would not use Loctite at all, if you mean the cyanacrylate glues

Locktite 242 is a thread locker, not a glue. http://www.loctiteproducts.com/threadlockers.shtml It takes 40 to 60 inch pounds (4.5 to 6.7 newton meters) of torque to break once cured. If too much is used such as coating the entire thread of the retaining ring with it, it will be more difficult to remove.
I use nail polish on retaining rings and 242 on case screws when needed.

 

[AgX]

Due to the option of special thread locking glues in general use the application of laquer to cover screw heads/nuts for locking has vanished.

If you still use laquer, what type do you use?

 

[Nodda Duma]

While convenient, I'd be careful with the loctite threadlocker .. it outgasses quite a bit.

NASA publishes outgassing data for many materials (epoxies, adhesives, RTV's, etc.) to aid in selection for space applications. I use this as a loose reference when outgassing in optical assemblies are a concern.

https://outgassing.nasa.gov/