Mamiya Sekor 180mm Front Element

Ariston · Mar 2, 2019

How do you remove the front element from a Sekor 180mm lens for an RB67? It seems the ring with the marking should come off firat; then there are notches for a spanning tool on the ring below that, but I cannot get the top ring to budge. Did Mamiya glue those down?

shutterfinger · Mar 2, 2019

Coat the outer edge of the ring with acetone, aka nail polish remover, and wait 5 to 15 minutes.
Basic camera repair technique as trim rings and fasteners are secured with a thread locker that is dissolved by acetone.

Ariston · Mar 2, 2019

Thank you - I wanted to do that, but it makes me nervous because the ring slopes toward the glass. I tried putting some acetone on carefully with q-tips, but I guess not enough is getting down in there. I'm nervous about dousing it, but I'll give it a try.

Ariston · Mar 2, 2019

I coated it pretty generously, twice, but it still won't budge. Bummer.

shutterfinger · Mar 3, 2019

Keep it moist for an hour or so. Sometimes they're stubborn. The acetone should not hurt the lens.

WilmarcoImaging · Mar 3, 2019

Do you have a rubber trim ring remover? Google it. Some inexpensive, hardware store plumbing rubber couplings can be used for this.

Ariston · Mar 3, 2019

Thank you Wilmar,

I did look into those, but they are around $40 unless you are buying for a 35mm camera lens. I reas someone used a rubber glove with a can, so I am doing the same with a cup. It is gripping pretty solidly, but I may visit the hardware store, as you suggest. I am also going to try and douse it for a long period of time todag, like shutterfinger suggests. Something is bound to work.

Ariston · Mar 3, 2019

Please excuse the typos; I am typing on a tablet.

shutterfinger · Mar 3, 2019

I've had to use penetrating oil on some stuck rings from the 1940's.
If the barrel is magnesium it will likely be a real pain. If aluminum it may be corroded in place.
If using nail polish remover there are two types, acetone and a synthetic. I do not know if the synthetic will dissolve the thread locker.
Another trick is soft heat. Heat you oven to 175° F to 250° F, when it reaches temperature place the lens in the center of the oven, close the door and turn the oven off. Leave the lens for 15 to 20 minutes, remove with a oven mitt as it will be warm. Repeat as needed to break the ring loose.

Keep the pressure even around the ring when trying to turn it.

Ariston · Mar 3, 2019

The oven trick is an interesting suggestion! I put quite a lot of acetone polish remover on it with no luck. I've decided to return it. I'm afraid to stick it in the oven (although I'm sure it woukd be fine), since I want to preserve the option to return it.

It's a shame because I would have liked to have gotten a longer lens for my RB for cheap, and this is about the only time I have felt I could actually clean fungus from a lens, since it seemed pretty straightforward to take it apart. I am not a camera tech.

Thanks to everyone for the help!

shutterfinger · Mar 3, 2019

Well, if it has fungus its likely the retainer ring is corroded in place.

tedr1 · Mar 3, 2019

I used a large diameter rubber bung that I bought on ebay for a few dollars they are sold for closing brewing flagons, size 12 I think.

M Carter · Mar 8, 2019

I got mine off - same lens - with a Fermco-style plumbing adapter. Just went to the hardware store and found the right size. Acetone on a front lens ring sound like a bad idea to me, there's no glue or anything in there. The mamiya repair manual says to use one of their rubber plug tools, but a rubber plumbing adapter worked just fine for me.

I've seen lenses where people (I assume) didn't know how to use the rubber plug, and they drilled two holes in the ring to get a spanner wrench on it. If all else fails, that will work too. I've had 2 RB lenses with fungus behind the front element and had them both like new in about 30 minutes.

Mamiya Sekor 180mm Front Element

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