Minolta M-Rokkor mount ring replacement/fix

[sanjin]

Hello all,

I'm writing here in the hopes that someone would be able to advise on a fix for a Minolta M-Rokkor 28mm f2.8 lens. I've bought this lens a while back with it having the dreaded 'spots' on the front element. This was successfully fixed with treatment by Will van Manen, who specialises in this. After getting the lens back I noticed something wrong when mounting it, and that is, that apparently the previous owner filed down the tab on the lens mount that tells the RF what framelines to engage. Why this was done, I don't know, but it's filed down so any camera will now show the 35mm as opposed to the 28mm framelines.

So my first thought was to replace the mounting ring with a cheap L39-M mount adapter with the holes drilled in the correct places, but this is not an option as the mounting ring also acts as the thread for the focusing helix. I figured finding a replacement rings is an option, so I've been asking around various camera repair shops and with prominent online specialists in Japanese photographic equipment, with no luck anywhere.

Which brings me to this post. Would anyone have any ideas either about a fix (permanent - I already figured out the option of taping the frameline-selector lever on my Hexar to the 28mm position for now) or where I might find a replacement mounting ring?

I am attaching an image of the element in question.

Thank you all!

 

[E. von Hoegh]

I don't see any evidence of filing in your photo.

 

[sanjin]

The image I attached is not specifically of the filed tab, but of the mounting ring in general, hoping someone might have a lead on one. Although, you can just make out the filing on the right side of the tab in the foreground (right of centre). There is a dark patch you can note despite the bad quality of the photograph - about 3mm was removed.

A better photograph is attached below.

 

[Ko.Fe.]

Rokkor-M 40/2 frame engaging tooth is often getting filed by owner to bring 35mm framelines on M Leica cameras instead of 50mm frame.

Don't know how easy is 28 2.8 on this regard, but getting this part (shown in OP) back on with 40/2 was and actually known issue. Not as easy as with any other lens I have to clean and re-lube.

Couple months ago I have my Rokkor-M 40/2 same kind of M-mount, focus assembly replaced with new one which I ordered from Australia. I was only able to find this part after I googled it. It came as eBay listing. Searching on eBay was not bringing it.

One lens shimming guru wrote what he used something like metal welding paste to restore the missing shape on the lens focusing cam. It might works with M-mount as well.

 

[Kino]

Cut and file a brass section to replace the missing area. You could either epoxy it in or drill and tap a screw to hold it in place.

 

[E. von Hoegh]

Cut and file a brass section to replace the missing area. You could either epoxy it in or drill and tap a screw to hold it in place.

Yes, if you have a set of #6 Swiss files, the skill to use them, and a .9mm or 1mm tap and tap drill - most don't. Another option would be to hard solder a piece of brass on, then file to shape but again, skills, and the probability of discoloring the mount. At least that area is away from the helicoid.