Repairing a Sigma 70-210 f/2.8

Thanks for the update .
While things have gone wrong , it's still very helpful to know what's happened ( and how ) so it can be avoided .
Some photos of it in the process of dismantling to gain access to it would still be helpful .
As would your thoughts on if there would have been a better way of doing it .

As I said , I still need to clean mine up !

Cheers .

Guys, I'm so sorry and extremely FAGGED OUT. I spoke too soon and worse: gave a misleading description. I've just freed myself of this worthless job that has consumed a number of days from me after maybe 10 straight hours (since I posted my last message). I've now destroyed any hopes of re-selling the lens (which is what I do). The damage to metal, and sadly glass, is too much to make it salable. I mistakenly said the lens didn't have to be stripped down; WRONG. I had forgotten that what I was looking at as the rearmost elements of the lens were actually the rearmost elements of the INTERNAL CHASSIS upon which the rest of the lens parts are attached. I didn't realise how deeply I'd gotten into this thing. There's still another group behind this group that actually carries the aperture blades itself. While trying to affix the aluminum ring back, I terribly scratched the glass on that difficult part we're talking about. Reassembling, I see it is very visible up till f4 after which the aperture blades cover it. Most tragically and without reason, I disassembled the frontmost elements that are mated by a helicoild path. I introduced dust, grease and all into it and was not able to put both back when it mattered. After maybe 4 hours and really messing up the whole area, I managed to force them together with a huge amount of particles between and they're jammed in and can't be separated (I used a vice, hammer etc). The guilty glass element seems permanently foggy but I did my best and it is now much better, but not 100% clear. Itself even managed to drop on the concrete floor and I almost fainted; but it didn't break. Quite a thin glass by the way

It's good your getting it sorted .
A few photos would be extremely helpful as if it's the same lens of mine , I've still to dig them out to clean them up .

I HAVE DONE IT! I came here for help, and now I'm the one who has provided the help! I feel glorious! Ok, I've taken the WHOLE lens apart only to discover I didn't have to. Right at the back of the lens there is an aluminum sealant to the very last lens element and it is the inner part of that group that gets hazy. I severely chipped some metal to succeed in this guesswork (informed as it was nevertheless). Just take the flattest, strongest metal you can find and pry from the inner edge of the outer reaches of the glass and pull the metal up and outward, going around as you do. Alternatively or in addition, stick the narrow strong metal inside the first gap (from middle) an try to pull up also. Don't tell me you won't scratch the metal because it's inevitable -- I don't think they made it to be removed. When you do that, the thin aluminium ring which acts to seal everything up would pop out, followed by an inner separator aluminum, and then the guilty element. THAT'S ALL! Ok, let me go now and see if the haze can be cleaned off. I feel very accomplished. My toughest project has now been carried out. I should add that I feel manual lenses are harder to dismantle than autofocus ones. That's my own experience from doing this thing on over twenty lenses. Cheers

Osi wrote: Thank you Neilt. So one has to join another online platform just to post a nondescript picture here. How great

Welcome to Dyxum Osi, I hope you will get your lens fixed.

And unfortunately this "free" site doesn't have the capability to store all the images shown here, cost and server size needed would be prohibitive. So you need one site for your images (there are plenty free ones) and then you'll get us for all the help the membership can provide here

Thank you Neilt. So one has to join another online platform just to post a nondescript picture here. How great

To post a photo you need to upload it to a hosting site such as Flickr .
Then copy and paste the BB code into your reply .