Removing outer casing of Nikon BD objective

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Oskar O
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Removing outer casing of Nikon BD objective

Post by Oskar O »

I have a Nikon CF Plan 20x BD inf, which I got for a reasonable price and want to use for testing my setup as well as later on do a little bit high mag photography (this is high mag at least for me). It's a BD version with EPI illumination channels, if that's what they're called; a ring around the lens assembly itself permitting to light the subject with frontal incident light with a suitable microscope. I don't have such a microscope and the casing gets in the way of subject illumination (I wasn't lucky enough to get an ELWD/SLWD version...), so I want to ask how to best remove the casing?

For illustration, here is the objective (I put some copyright text, since I don't want to see this pic in eBay listings... hope you'll forgive me the crappy light setup though :) :

Image

You can clearly see the hollow area between the front element and the out shell. Here the objective with the outer shell with the labels removed:

Image

But how to remove the next layer? If you look carefully, there's a hole in the threads, revealing another set of threads beneath. This would lead me to think that the thing separates just above the threads. I didn't have serious tools at home to try to force it and it's tight so it wouldn't budge, but I thought that getting some hints on which part should separate from what and how would be very useful instead of just going down the brute force approach.

Any help welcome,
Oskar

PS. seems I can drop the tube lens focal length quite low before getting vignetting... will be interesting to see where this will lead...

rjlittlefield
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Post by rjlittlefield »

I do not have this exact lens, but your description is correct for the two BD's that I do have. The inner barrel simply unscrews from the body of the objective. There are no locking devices such as setscrews.

However, on one of my units, the threads of the inner barrel were sealed with a material like nail polish. I could not get it loose with just force.

Instead, I softened the sealant by placing a tiny amount of ethyl acetate (about 1 microliter) on the joint between barrel and body, and allowing it to wick in and sit for a minute. When the sealant was softened, the barrel removed easily.

There is a discussion of this issue here: http://www.photomacrography.net/forum/v ... hp?t=11933.

--Rik

Choronzon
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Post by Choronzon »

That's exactly how you do it, or if you're being paid by the hour, you can use alcohol :lol:
The threads are locked with 3 bond, because the inner shell adjusts the intensity and eveness of the darkfield illumination, depending on how much it is screwed in or out.
I am not young enough to know everything.

AndrewC
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Re: Removing outer casing of Nikon BD objective

Post by AndrewC »

Oskar O wrote:...I put some copyright text, since I don't want to see this pic in eBay listings... ...
In that case you should put your text where it isn't easy to paint out :) Use a very large font, make it about 15% solid and plaster it over the centre of the image.
rgds, Andrew

"Is that an accurate dictionary ? Charlie Eppes

Oskar O
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Post by Oskar O »

Aah... Now I see! I have to try with a tiny bit of solvent. The nail polish removers that I've seen are mostly acetone, I guess that should work, but I'm not a chemist. It's a bit of a challenge to say where exactly the seam is, since the pieces sit so well together, but I guess it's just above the thread that's fr holding the outermost piece.
AndrewC wrote: In that case you should put your text where it isn't easy to paint out Smile Use a very large font, make it about 15% solid and plaster it over the centre of the image.
You are of course correct, but I was satisfied to just make it clear that these pics are not in the public domain. Now if someone removes the texts and reuses them then that's just bad manners and against the law :)

Oskar O
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Post by Oskar O »

I got it opened. It took some solvent, a needle to remove glue residue, force and patience. The threads are well made and fine, fitting together fairly precisely. Here's a picture:

Image

Now it's a piece of cake (in relative terms...) to light the subject :)

I'm tempted to post some pictures, but since the objective was taped to the tube lens, and I didn't have a good setup anyway, I'm holding back. It does however seem that the tube lens FL can be fairly low while still keeping vignetting at bay (this with a crop sensor), so there seems to be pretty good potential in various Nikon CF Plans...

keks
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Post by keks »

According to Rik's advice I am adding my experiences from opening a Nikon BD Plan 60 0.7 ELWD here. It's an old thread but still relevant topic I guess.

In this case both threads were secured with glue, thus I could not even remove the outer case by mechanical force only, not even with the cable glands you see below.

For softening the glue ethyl acetate came into my mind because its a common solvent in many glues. When applying the ethyl acetate (I applied plenty) it readily crawled into the thread and after about 3 minutes I could open the outer thread with little force, however the cable glands were still very helpful.

For opening the inner thread the procedure was exactly the same, but I recommend to have a close look at the 2 little holes in the outer thread: I found some metal chips in there, which I removed with a needle. If not removed they may damage the thread. Besides, I think these holes are helpful for applying solvent.

At last, for cleaning the threads I soaked them with the ethyl acetate (which effectively softened the glue) and removed the softened glue with tissue paper.

PS: nail polish remover should work also, I have one here that consists of ethyl acetate and alcohol.
Last edited by keks on Sat Feb 18, 2017 9:21 am, edited 1 time in total.

keks
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Post by keks »

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keks
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Post by keks »

@ChrisR: Actuallly I also have a BD Plan Apo (40x 0.80), I came across it before I got the BD Plan 40x ELWD and could not resist.

I am very sure that the thread to remove the outer case is in the same position as for all the other BD Plans - just beside the knurling. But removing that outer case does not at all change the lighting situation.

Beside that I know nothing, so im hesitant trying ....

jkbordoloi
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Re: Removing outer casing of Nikon BD objective

Post by jkbordoloi »

Can someone tell me what that tool is? I am having a hard time opening the casing.

PeteM
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Re: Removing outer casing of Nikon BD objective

Post by PeteM »

jkbordoloi wrote:
Thu Aug 03, 2023 3:55 am
Can someone tell me what that tool is? I am having a hard time opening the casing.
The picture above your question is a pair of plastic conduit fittings. Clever idea. You should be able to find them in the electrical supply area of any large hardware, electrical, or home supply retailer. Some other approaches:

- A pair of soft jaw connector pliers can be used. Some versions are also available for optical and camera work.

- A rubber-faced strap wrench can work.

- A hole the size or slightly smaller than the O.D. of the item you wish to grip can be bored into a piece of wood. Then saw through the middle of the hole and clamp the two pieces around to make your own soft jaws sort-of-vise. A wide kerf in the saw cut allows you to grip the part if the hole is on size.

- If you know someone with a metal lathe and an assortment of work-holding collets, these are ideal for very firmly gripping parts like this without marring them.

jkbordoloi
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Re: Removing outer casing of Nikon BD objective

Post by jkbordoloi »

PeteM wrote:
Thu Aug 03, 2023 7:46 am
jkbordoloi wrote:
Thu Aug 03, 2023 3:55 am
Can someone tell me what that tool is? I am having a hard time opening the casing.
The picture above your question is a pair of plastic conduit fittings. Clever idea. You should be able to find them in the electrical supply area of any large hardware, electrical, or home supply retailer. Some other approaches:

- A pair of soft jaw connector pliers can be used. Some versions are also available for optical and camera work.

- A rubber-faced strap wrench can work.

- A hole the size or slightly smaller than the O.D. of the item you wish to grip can be bored into a piece of wood. Then saw through the middle of the hole and clamp the two pieces around to make your own soft jaws sort-of-vise. A wide kerf in the saw cut allows you to grip the part if the hole is on size.

- If you know someone with a metal lathe and an assortment of work-holding collets, these are ideal for very firmly gripping parts like this without marring them.
Thank you for your reply. I took my objective to our workshop (at work). Turns out the inner casing was cross threaded hence had to use something with brut force to open it. There was some serious damage to the casing however, the inner contents were free from any damage. Resell value has markedly reduced now....but hey I can use it for my work. A lot to learn...

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