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Dismantling a lens


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#1 Bill DiPietra

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Posted 23 June 2014 - 09:54 AM

I know there was a recent thread regarding "Building a lens" on here, but I've always wanted to dismantle one to see the inner transmissions/workings of it.  Of course, each one is different, but I wouldn't need anything high-end as I wouldn't plan on putting it back together for use.  I tried this many years ago with a cine zoom lens that someone was about to throw out, but I was stopped cold since I just didn't have the tools I needed to open it up.  Is this do-able or would I need access to a shop?

 

As always, thanks for any help.


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#2 Stuart Brereton

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Posted 23 June 2014 - 11:09 AM

Generally all you need is a lens wrench and a set of jeweler's screwdrivers. 50mm stills lenses are cheap and plentiful on ebay. A search for 'parts or repair' should find you s suitable subject.


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#3 Freya Black

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Posted 23 June 2014 - 11:26 AM

I've actually got by with a pair of scissors instead of a lens wrench before now! ;)

You might need to have the right pair of scissors though.

Like with all things, some lenses end up being able to get into than others as some are more tightly together.

 

Freya


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#4 Bill DiPietra

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Posted 23 June 2014 - 07:34 PM

Cool.  Thanks!


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#5 Simon Wyss

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Posted 24 June 2014 - 12:30 AM

There are lenses that are very hard to come by. Glued plastic parts and such

 

If you choose something simple, entirely metal, the time invested may be rewarding. It’s a good feeling to have it back together as clean glass and freshly lubricated mechanics.

 

http://forum.mflenses.com


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#6 Bill DiPietra

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Posted 24 June 2014 - 07:52 AM

Thanks, Simon!


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#7 Stuart Brereton

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Posted 24 June 2014 - 10:03 AM

Old lenses often have screws held in place with a drop of clear nail polish. A q-tip dipped in Acetone will free them up.

 

Lots of good advice here http://mattsclassicc...repairtips.html


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#8 Bill DiPietra

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Posted 24 June 2014 - 01:27 PM

Oh wow.  That's an awesome site!  Thanks again!


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#9 Dom Jaeger

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Posted 24 June 2014 - 09:33 PM

Hi Bill,

pulling apart lenses is one of the best parts of my job, a bit like solving puzzles, especially when you don't have drawings or disassembly instructions. There's great satisfaction when you finally work out the trick that unlocks the next layer. Sometimes you need to start from the front, sometimes the back, sometimes both!  Sometimes a lock ring doesn't have notches for a lens wrench to slot into, and you need to use circular rubber grips. I've made about 20 of those, of different sizes, using O-ring rubber cut and glued to the end of tubes. But certainly the main tools are jeweller's screwdrivers (or occasionally mini allen keys) and a lens wrench. You can buy lens wrenches on ebay for next to nothing these days. If the lens is junk I guess scissors would work too, but be careful not to cut yourself, sometimes undoing a lock ring can take a bit of force. To safely remove glass elements you need suction cups, but that's probably beyond what you're interested in. Some other tools I personally find very useful are tweezers, magnifying loupes, toothbrushes, cotton buds and most importantly a compartment tray to keep all the bits in. You can store the bits in sequence to make it easier to reassemble later. 

 

A drop of acetone on tiny screw heads will soften any locking varnish, as Stuart mentioned. Lock rings and other threaded connections may also be varnished in, again a drop of acetone run into the join will help loosen things. Just be careful of some plastics or painted surfaces when using acetone. Some stills lenses have screws hidden under a decal glued on over the front ring.

 

Be careful not to damage the heads of tiny screws, once the slot or cross or hex is rounded off the only recourse is to drill the screw out. If a screw won't turn it's best to try some more acetone or even a bit of heat from a hair dryer rather than force it. Though I suppose it doesn't really matter if you're just playing with junk lenses.

 

Here's a photo I took recently of a Kowa anamorphic lens I spent some time overhauling, it has very clever dual focus mechanics where the focus ring moves both a middle anamorphic element via a cam and the rear prime via a helical thread at the same time:

 

Kowaanamorphicdisassembled_zpse6f0f634.j


Edited by Dom Jaeger, 24 June 2014 - 09:35 PM.

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#10 Stuart Brereton

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Posted 25 June 2014 - 01:23 AM

pulling apart lenses is one of the best parts of my job, a bit like solving puzzles, especially when you don't have drawings or disassembly instructions. 

 

I love pulling them apart - it's putting them back together that's the hard part :)

 

I just declicked and cleaned a set of Asahi Takumars. They're tough to work on because you have to go in through the front and remove just about everything to get to the iris. Great sense of satisfaction when I'd finished, but I don't know that I could do it on a regular basis like Dom. My nerves would be in tatters.


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#11 Freya Black

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Posted 25 June 2014 - 10:40 AM

Some other tools I personally find very useful are tweezers, magnifying loupes, toothbrushes, cotton buds and most importantly a compartment tray to keep all the bits in. You can store the bits in sequence to make it easier to reassemble later.

 

I already thumbed you up, but I still want to say "Great Posting Dom!!!" :)

 

Anyway I use the cotton buds too, but there are some great tips in your list! What do you use the toothbrushes for tho? Not for polishing the glass I assume! ;)

 

Yeah you need to always be careful with scissors and I found that you had to have the right pair to make it work too but I happened to have a good match. I'm going to get a proper lens wrench shortly tho because I got into it all a bit too much!

 

The other thing I use is the rubber plugs that go in sinks to grip and turn those lens fronts without any normal way to turn. You know the ones I mean I'm sure!

 

Wow that Kowa anamorphic lens is quite hardcore! :) I wouldn't be able to go there!

 

That reminds me, the other thing is that primes are generally easier to work on than zooms depending on what you are doing.

 

Also Canon FD glass is really difficult to get apart in my experience and the glass is often encased in wierd plastic that isn't like normal plastic but more like bakelite... only modern bakelite... from another planet. It seems to be stronger than some metals even! I suspect they developed it from something they found in a crashed saucer.

 

Soviet stuff on the other hand is easier to take apart and fix and modify.

 

Freya


Edited by Freya Black, 25 June 2014 - 10:41 AM.

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#12 Bill DiPietra

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Posted 25 June 2014 - 06:13 PM

Thanks, Dom!  That post is a keeper!


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#13 Chris Millar

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Posted 25 June 2014 - 06:46 PM

I went through a bout of this a few years back - my first was a Bolex PTL zoom, trying to access to past the auto iris trying to get a bit of paint fleck or whatever it was sitting on an element...  Quite a challenge was the auto iris, I got there and back without too much force, and discovered a missing screw in the process, once replaced the mechanism worked much better. The seller protested that it had never been opened 'ever', which I knew was bs...  However I do wonder if I did something, to affect the light meter, it seemed fine, but... 'I don't know what I don't know', if ya know what I mean :D

 

Next up, cleaning oil off an element from a Preset Switar 75mm - ha!  no way, not without proper tools, that ended up with a tech.


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#14 Dom Jaeger

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Posted 27 June 2014 - 02:31 AM

What do you use the toothbrushes for tho? Not for polishing the glass I assume! ;)

 

Toothbrushes are great for cleaning focus threads, gear teeth, little channels and such.

 

I like your idea of using bath plugs as gripping tools, very creative! There's probably a whole tool set you could fabricate from things you find in the bathroom..  :)


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#15 Robert Glenn

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Posted 21 May 2015 - 08:24 PM

I have 2 questions:

1-has anybody disassembled a switar 10mm RX?

2-Anybody have a source for tiny replacement grub screws?

 

thanx


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#16 Mark Dunn

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Posted 22 May 2015 - 04:02 AM

Based on experience, don't unscrew a multiple helicoid thread fully. They are impossible (in my case) to re-engage.

If you decide to go ahead, scribe a reference mark so that you can re-engage the correct thread otherwise the focus scale will be out of whack.

I expect only the larger lenses have these- mine was a 6x9cm format 90mm. (Mamiya Press)


Edited by Mark Dunn, 22 May 2015 - 04:04 AM.

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