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  #1  
Old 19th July 2022, 01:10 PM
alexmuir alexmuir is offline
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Default Lens maintenance

I have a convertible Schneider 210mm lens which requires some internal cleaning. The problem is on the internal surface of the front element. I’m sure it will clean easily if I can get in at it. The glass is held by a large retaining ring with two notches. I have an adjustable lens spanner which I have used to try to unscrew the ring. Unfortunately, it won’t budge. I don’t want to apply too much pressure, in case the tool slips. Is there any technique, or trick I can try, or is it simply a question of brute force?
Thanks. Alex.


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Old 19th July 2022, 09:33 PM
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Reginald S Reginald S is offline
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No brute force, please.

An old mechanist's trick:
You can try to turn clockwise (tighten) first before loosen the element.

You also could work with temperature:
- bring the lens to the refrigerator and then to the freezer.
Don't forget to protect the lens against condens water.

If freezing doesn't work, you can change to carefully heat up the lens in the ofen - 50 or 60 degrees Celsius max.

Another technique is a rubbler matte on the table:
Press the delinquent on the rubber and try to loosen in this way.

After all, without any success, we could talk a bit about controlled force :-)
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Old 20th July 2022, 07:04 AM
alexmuir alexmuir is offline
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Thanks Reginald! I will try your suggestions later today.
Alex


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  #4  
Old 20th July 2022, 09:49 AM
John King John King is offline
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Default Removing a locking ring

I would not attempt to remove the ring with what you have got, there is too much of a risk if it slipping and causing damage and as sure as God made little apples it will be to the lens surface. You really do need an appropriate tool.

The description that you give suggests to me that you need something like a 'peg' spanner. Basically they are a tube that is to large enough to fit over the end of the ring you are trying to remove but will have at two 'pegs' standing proud from the end and these are fitted into the the two notches on the ring you are trying to remove.

How long it has been there may dictate how much effort you will need to remove it.

Then you may need something to hold the lens steady whilst you twist the tube with the pegs engaged in the slot. that sounds to be a two man task to be able to do it safely and without damage.

Depending on the age of the lens, when it was constructed the company may have used some sort of thread locking compound to stop it coming loose which again would make the ring difficult to loosen.

Given the dimensions of the lens and in particular the distance across the threaded area, plus the size and positions of the slots it would not be difficult for an engineer to make one for you.

Just a thought, occasionally manufacturers made locking rings with a left hand thread which loosens in the opposite direction that you may think.
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Old 20th July 2022, 10:18 AM
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B&W Neil B&W Neil is offline
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Default Rubber Matt

The rubber matt idea certainly works but finding a suitable matt can be hard. I ended up cutting a section out of an old rubber wellington boot. Used boot lining side down on a work surface with the lens pressed hard against the rubber outer side did the trick. It now resides in my lens repair kit box and I use every time I need to dismantle a lens.

Neil.
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  #6  
Old 20th July 2022, 03:06 PM
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I have a set of rubber pads that range in diameter from 37mm up to 86mm. They came in a set of seven and combine two diameters in one block. They are concave in shape so as to provide room for a protruding element.Those now available for sale on eBay are of a different design and have a large hole in the centre to allowance clearance.

https://www.ebay.co.uk/sch/i.html?_f...fLoc=1&_sop=15
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Old 20th July 2022, 03:39 PM
alexmuir alexmuir is offline
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Thanks for all the replies and suggestions. I tried Reginald’s first suggestion of giving it a turn clockwise first, then anti-clockwise to unscrew. It came free first time. I then replaced the lens spanner with a wooden cocktail stick to complete the process of unscrewing the ring. I have cleaned and reassembled the lens, and it looks great. I was intending selling it, but may give it a try to assess its performance now it is clean.
Thanks again to everyone, and especially Reginald for that very useful tip.
Alex


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  #8  
Old 20th July 2022, 09:07 PM
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Reginald S Reginald S is offline
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The first rule of old mechanicks:
"It doesn't work" is an unknown phrase :-)

I don't know much Schneider convertible lenses.
Is this an old Symmar?
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Old 20th July 2022, 09:49 PM
alexmuir alexmuir is offline
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Yes. I’ll try to add an image

I think you remove the front cell to convert to the longer focal length. I didn’t have enough bellows extension available before, but now I have an extendable monorail which should work. I think I’m correct in saying that it is really meant as a ‘standard’ lens for 5x7” cameras, where the secondary focal length would be more relevant. I like the image from the 210mm on 4x5”. It hasn’t seen much use lately, but now it’s cleaned I fancy taking the camera out and about. It’s a Horseman monorail, so not very easy to carry around!
Alex.


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  #10  
Old 20th July 2022, 10:41 PM
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f12 is really dark.
These convertible lenses are fine for this one photo were you definetively will need a longer lens, but don't expect too much concerning typical large format quality of the rear element only.

My triple convertible Turner&Reich goes up to 570mm, but for 5x7" I prefer as a standard my old Xenar 210mm (Compound shutter) which is sharp if necessary and mild if wanted, plus a 360mm Tele Xenar which isn't just a longer lens but a real Tele construction with it's advantages.
Both are excellent portrait lenses, too.
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