Lens Thread Lubrication

[Two23]

I took all my larger brass lenses apart (two Petzvals, Velostigmat, early pillbox) and noticed the threads on some were very gummy. I cleaned them off using a thick paper towel that had some gun lube (CLP, petroleum product) on it. I then carefully wiped the threads so there wasn't any excess CLP oil on them. Lenses unscrew much easier now. I was wondering if there was a better product to use on these threads? The idea is to keep them from sticking. I had thought of a little white lithium grease. It seems pretty stable. My worry is something will react with the brass and make a bigger mess.


Kent in SD

[Jac@stafford.net]

A thin application of white lithium grease is stable. I recommend it.

FWIW - and you know this, but for the rest, powdered graphite is death for camera gear - it manages to migrate to lens surfaces and is a total b*tch to eliminate.

[LabRat]

First thing is to try to clean threads of old lube, debris, and grime... A little lighter fluid on a q-tip will start the process, and a toothpick or dull needle to get to the bottom of the threads... If the threads are rough, sometimes a tiny bit of toothpaste rubbed there helps, but be careful not to let it spread around... (And the fluoride in it will prevent oxidation on aluminum surfaces...)

A good clean photo gear grade grease is "Super Lube" silicone/teflon from your hardware store... Does not dry up, inert, and is clean to the touch when thin... A little dab will do 'ya...

Steve K

[Steven Tribe]

My view about difficult threads, especialy on hand-cut threads on Petzvals, is that lubrication is not the answer.

Whenever I find resistance, I do a mini thread cutting operation. That is, I apply, fine automative value seating grinding paste to the thread and screw in gently. Like thread cutting, I turn perhaps 20 degrees when there is obvious resistance and turn backwards and forwards many times until the thread eases up. I usually clean out the paste about halfway through and start again with new paste. It is surprising the colour change the old paste shows! Something like an old toothbrush is necessary to remove all traces of the paste, brass powder and copper and zinc oxides.

I am certain that the main cause of tightness is that the brass barrel is no longer completely round - but don't try and alter the barrel!

[Two23]

I am certain that the main cause of tightness is that the brass barrel is no longer completely round - but don't try and alter the barrel!


I think you are probably right over all, but one lens did seem to have gummy threads. Will try the suggestions above.


Thanks,
Kent in SD

[Jac@stafford.net]

Steve, your valve grinding paste and technique is solid gold. Thanks. I had forgotten it.
As is often, the missing ingredient is patience on my part.

[Bernice Loui]

+1

This is essentially thread lapping to match the internal-external threads. Over doing this will result in a sloppy fit and excessive play between parts involved. It is important to clean out every last bit of lapping compound if this is done as lapping compound remains abrasive for as long as the stuff is between the threads and will continue to grind on the threads each time the threads are moved.

Alternative, clean out the threads really well then check rotational feel with the threaded parts joined. If rotation is smooth, do not apply the lapping process as it would not be needed. If there is sticking and irregular friction/smoothness between parts, then consider applying the lapping process.

*Know once material is removed, putting material back is really, really, really difficult and this is would be by the thousands of an inch.


Do use a lubricant, it damps thread movement, reduces wear and helps with smoothness of rotation. If the parts involved is brass, consider using Dupont Krytox a teflon based grease that is inert, non-crossive and does not dry out. Krytox was originally developed to lubricated moving parts in space flight's hard vacuum environment. Krytox is not compatible with aluminum parts and galling will result.


Bernice





My view about difficult threads, especialy on hand-cut threads on Petzvals, is that lubrication is not the answer.

Whenever I find resistance, I do a mini thread cutting operation. That is, I apply, fine automative value seating grinding paste to the thread and screw in gently. Like thread cutting, I turn perhaps 20 degrees when there is obvious resistance and turn backwards and forwards many times until the thread eases up. I usually clean out the paste about halfway through and start again with new paste. It is surprising the colour change the old paste shows! Something like an old toothbrush is necessary to remove all traces of the paste, brass powder and copper and zinc oxides.

I am certain that the main cause of tightness is that the brass barrel is no longer completely round - but don't try and alter the barrel!

[LabRat]

My view about difficult threads, especialy on hand-cut threads on Petzvals, is that lubrication is not the answer.

Whenever I find resistance, I do a mini thread cutting operation. That is, I apply, fine automative value seating grinding paste to the thread and screw in gently. Like thread cutting, I turn perhaps 20 degrees when there is obvious resistance and turn backwards and forwards many times until the thread eases up. I usually clean out the paste about halfway through and start again with new paste. It is surprising the colour change the old paste shows! Something like an old toothbrush is necessary to remove all traces of the paste, brass powder and copper and zinc oxides.

I am certain that the main cause of tightness is that the brass barrel is no longer completely round - but don't try and alter the barrel!

I have done this, but there are dangers...

If the thread fit is tight (but now clean), it often indicates that it is out of round, so if there is a binding point, it will tend to cut more there, and at other points of mating, and as the thread is slowly making it's way down, it will cutting more at the outer areas of the threads (increasing the outer diameters and cutting tapers more), and the leading edges of the male thread will be pushing up a "hill" of compound in front of the threads, so there is a strong chance that this debris will clog the thread possibly binding the two parts together (like introducing a very fine sand between them) possibly forcing them to crossthread, and in the end there might be a sloppy fit between them...

If attempted, use the absolutely smallest amount of grinding medium (like a pinhead amount) keep it lubed with lighter fluid, and don't overdo it... Usually it is just some old paint or sticky oxidation, or out of round... (You CAN make it worse by this process, as excessive torque on the barrels can further bind them or tweak them out of round!!!) If you can strip the components from the threaded parts, a bath in a ultrasonic cleaner can deep clean the threads...

Be warned, and don't ask how I found out...

Steve K

[Sfroza]

Personally, I'd stay away from having or using any product that contains silicone anywhere near optics. Silicone migrates readily onto any surface, with disastrous results with optics. The solvents that are used to remove silicone will damage a lenses coatings.

Michael