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View Full Version : Lens-cap STUCK on old Jamin-Darlot -- advice for removal?



Kiev
21-Apr-2015, 18:12
Hello All!

First time post from new member with request for advice: I recently acquired an old Jamin-Darlot cone centraliser, portrait/landscape (vis a portrait/vis a paysage) lens, c. 1860. Looks to be in good condition, mechanism works smoothly; but the lens cap is stuck, seemingly impossible to remove. In my research I've been unable to determine if the cap is threaded or simply a push-on sleeve. Glass appears to be in pretty good shape, but I can't be sure until I can get the cap off and see through the barrel. (See pix below.)

Any thoughts, advice, ideas, or suggestions on how best to proceed with lens-cap removal? Or perhaps recommend a professional service that might be better equipped to effect removal? (I suspect that the cap is not threaded, and it's merely the 150 years of patina and gunk that's frozen it in place, so maybe with the right tools . . . ? )

Many thanks in advance for your time and expertise! Great forum here; learned a lot already!

Kiev


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goamules
21-Apr-2015, 19:23
I've never seen one on the rear. But have seen lots on the front, and I have one. They are just a friction fit. Try gently heating it up with a hair dryer. Then grab with a rubber grip pad, and try to gently turn it a little while pulling. Don't unscrew it counterclockwise! You don't want the rear element unscrewing and coming off in the brass cover, or you'll never get it out.

Kiev
21-Apr-2015, 19:56
Hello, Garrett --

Ah-a! So, at some point somebody must've forced the lens-cap onto the rear of the lens; that's probably why it's stuck: capped on the wrong end.

In any case, your idea intrigues me; just might work, too! But will the heat adversely effect the glass . . . ? Meanwhile, it's very helpful to have confirmation that it's a friction fit cover -- many thanks for that infomation!

Now when you say counterclockwise, the orientation is when looking down on the cap, correct?

Kiev

Steven Tribe
22-Apr-2015, 01:33
I use heat to loosen brass on a regular basis and there is absolutely no problem with Garrett's solution.

Let's hope the cap hasn't been forced on to cover up some defect!

My approach would be to drop the gentle warming, but go over to a small blow touch. The cap is very thin with a super fast conductivity of heat and will be over 100 deg C in seconds. And the cap provides automatic projection from stray heat reaching the lens surface. I would spray with impregnating fluid, both before and after heating (if it doesn't come of first time) - a few small flames, and fumes, won't be of consequence.

Regular Rod
22-Apr-2015, 03:34
I use heat to loosen brass on a regular basis and there is absolutely no problem with Garrett's solution.

Let's hope the cap hasn't been forced on to cover up some defect!

My approach would be to drop the gentle warming, but go over to a small blow touch. The cap is very thin with a super fast conductivity of heat and will be over 100 deg C in seconds. And the cap provides automatic projection from stray heat reaching the lens surface. I would spray with impregnating fluid, both before and after heating (if it doesn't come of first time) - a few small flames, and fumes, won't be of consequence.

+1, a cook's blow torch is about the right size and intensity. Circular wafting is the way.

RR

alex from holland
22-Apr-2015, 06:16
Never seen a cap at the back of a cone lens.
There is only just a few mm where that cap could hold on the lens. so it makes no sense to mount one
You should be able to take of the black back part (cone). This just to have a look inside.

again, where that cap is on, there is only a few mm to hold it.

Alex

DrTang
22-Apr-2015, 06:51
hammer
















hahhah - just kidding

Jerry Bodine
22-Apr-2015, 11:37
I just stumbled into this thread. Pardon my ignorance, guys, never having seen such a lens. But, looking at the first pic, it seems to me that the cover is cylindrical and is inserted into the INSIDE of the rear element (cone). So applying heat to the cover would only make it tighter, in which case it would be more sensible to apply COLD (maybe ice cubes in a ziplock bag) to the cover to shrink it and get it to release, while grasping the "grip surfaces" on the cone and cover to wiggle it off. Or not!

Kiev
22-Apr-2015, 12:47
Thank you all for your input! I've provided a few more photos of the lens to better show the cap and elements in detail. (See below.)

Steven: I think heating the cap will work, but using a torch seems a bit overkill -- I'd hate to inadvertently damage the glass! Hopefully, the cap will slide loose with less extreme measures. In any case, I can try with a conventional hair-dryer first, and then go up from there.

RR: Ditto.

Alex: I believe you are correct. I've seen pictures of similar assembles, and the lip didn't appear that wide -- it's amazing how tight a tension just a few millimeters can exert on that cap!

Jerry: The cap is definitely over the end of the opening. In fact, it was slightly cockeyed when I found this lens; and while I am unable to twist it off, it did tap down easily enough into a flush position (hence I suspected this was a case of stripped threads).

DrT: Right. :)


Meanwhile, I've contacted S.K. Grimes about cleaning the glass lenses. They're willing to have a go at the cap, as well; but I'd prefer to get the thing off myself so I can properly determine if the lenses are worth investing in a pro cleaning. Will keep you posted . . .

Again: Many thanks for your assistance!


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Steven Tribe
22-Apr-2015, 13:20
Thank you all for your input! I've provided a few more photos of the lens to better show the cap and elements in detail. (See below.)

Steven: I think heating the cap will work, but using a torch seems a bit overkill -- I'd hate to inadvertently damage the glass! Hopefully, the cap will slide loose with less extreme measures. In any case, I can try with a conventional hair-dryer first, and then go up from there



Meanwhile, I've contacted S.K. Grimes about cleaning the glass lenses. They're willing to have a go at the cap, as well; but I'd prefer to get the thing off myself so I can properly determine if the lenses are worth investing in a pro cleaning. Will keep you posted . . .

Again: Many thanks for your assistance!






Warming the edge of the thin brass cap with a flame for a fraction of a second is the best way to create a marked temperature differential between cap and the thicker brass underneath. This will loosen the cap. Warming slowly with an air blowing system will ensure that the whole assembly (including the two rear lenses!) will gradually warm up with very little temperature differential between the end section and the cap.

I am not sure what you mean about "cleaning .. pro cleaning"? There is no cleaning process that Grimes can do that you cannot do. If there is mechanical damage on the rear pair edges or scratches on the final rear surface - then they will always be there. Mostly likely with this model is advanced edge separation with the front achromat - but this is easily solved without bothering Grimes and the others.

goamules
22-Apr-2015, 13:20
There is no way you need to go to Grimes to clean the rear elements. They're just two pieces of loose glass. No coatings, nothing to disassemble, other than getting that cap off, then unscrewing the inner retainer. When you are removing them, make sure you have the separator ring between them. When you reassemble, put the two most severely curved surfaces (one convex, one concave) "nested" to each other, separated by the ring. The thinner glass is in the rear.

For cleaning, do them one at a time in a tupperware full of warm (not hot) soapy water. Rinse, and dry. Don't rub hard, or the grit will scratch the softer glass of one lens. But you can get them like new with some water.

goamules
22-Apr-2015, 14:07
I see there is a lip on the brass cap, and there is another at the back of the cone. You could try gently prying, with a block of wood about the size of the gap. Use a fulcrum, and you can move the cap, I bet. Just go gently, it's just seized from being on there a while.

Kiev
22-Apr-2015, 14:35
You guys are awesome!

Steven: Now that makes perfect sense! Hadn't considered it that way -- thanks for clarifying.

Goamules: Hmmmm, might be on to something there. As I don't have a torch handy, maybe a bit of clever jimmying will do the trick!

As for cleaning: I'll decide once I get the cap off, and see what's what. Of course, I'd rather do the work myself and save some $$$.

Meanwhile, what are your thoughts on polishing? Generally I prefer preserving any patination that shows the history, but this sure would look pretty all polished and bright!


Kiev

pierre506
22-Apr-2015, 14:50
Polishing?!?!?!
No more comment~

brandon13
22-Apr-2015, 15:48
Please do not polish of that beautiful Patina. Please.

Jim Noel
22-Apr-2015, 15:56
I've never seen one on the rear. But have seen lots on the front, and I have one. They are just a friction fit. Try gently heating it up with a hair dryer. Then grab with a rubber grip pad, and try to gently turn it a little while pulling. Don't unscrew it counterclockwise! You don't want the rear element unscrewing and coming off in the brass cover, or you'll never get it out.

Oops, wrong direction. Cool it sown and it may even fall off.

goamules
22-Apr-2015, 17:07
Let us know if you got it off. Have you tried the hair dryer and twisting clockwise yet? If that doesn't work right away, spray a little fine oil, like CLP Break Free (from Walmart) in the crack where the bottom of the cap is, let it sit overnight. Then try again in the morning.

Kiev
2-May-2015, 13:34
Hell again, all!

Well, I finally got the cap off! In the end, it was surprisingly easy to pop-off -- just needed a little heat and a wooden spoon to tap it off.

Interestingly, the brass lans-cap appears to have the original cotton dust-liner inside-- and, of course, the cap fits perfectly over the correct end of the lens!

I would post updated pix for you to see, but rather frustratingly, this website will not allow me to post any more pix to this thread (at every attempt, the site claims that even the smallest files are over capacity).

In any case, many thanks again for your kind advice and encouragement!


Best,

Kiev

prendt
2-May-2015, 14:36
Hell again, all!

Well, I finally got the cap off! In the end, it was surprisingly easy to pop-off -- just needed a little heat and a wooden spoon to tap it off.



Kiev

Am I the only one disappointed? You could have been the first person on the forum who got a lens cap off a lens with a blow torch - and you blew it !

Kiev
2-May-2015, 15:53
Am I the only one disappointed? You could have been the first person on the forum who got a lens cap off a lens with a blow torch - and you blew it !

prendt: Haha! Actually, a torch probably would've singed the cotton lining inside the cap.

But you're right: the blow-torch record is yet to be made -- so, you're free to give it a shot!

goamules
4-May-2015, 08:08
Good deal! Yeah, I cringed when I read someone suggesting a blow torch...too hot and risky on old brass and glass.

These were very popular lenses in the 1850s and 1860s, and are good ones. Enjoy it's use, and let's see some photos taken with it.

Kiev
4-May-2015, 09:10
Steven Tribe: Thank you for this information. I managed to get the cap off in the end -- without heating. I have since taken the lens apart and gently cleaned the glass elements, all three appear to be in good shape; and so is the brass body. I didn't notice any edge separation. (I would post pictures, but it would appear that I have reached my limit for posting photos to this thread.) Thanks for your input.

Kiev