It looks like you are grinding off quite a lot of material from the new EF mount: the flat outer part? This allows the new mount to sit inside the "blue" ring? (in my illustration)...
The one marked blue may look like the silver ring on the 58/1.2, but it is not. It serves an entirely different purpose. Seeing the "silver ring" and assuming the lens is constructed like the 58/1.2 is a mistake. It is nothing like that, and most of these lenses are nothing like the 58/1.2 in this respect. The conversion process is significantly different.
The ring marked green is not a ring. It is the actual mount base. The silver ring is just a shroud over the mount base. It is the mount base that needs to be reduced (see Dmitry's second shot, it is silver because it has been reduced and the bare metal is exposed).
Like I said, completely different than the 58/1.2.
* The "yellow" stuff gets discarded, no? Yes throw it away (you need to unscrew it from the inside - four screws)
* The "red" rear element rings gets filed down? Yes as low as possible, actually i unscrew holding ring and glue the back lense in place - the answer for -Ed
* The "blue" ring stays but gets shaved for infinity focus like we all do on the 58/1.2? it stays as is (maybe it will need a bit to sand) and take a role of outer surface of original M42 adapter - where you drill a hole for EOS bayonet stopping pin.
* What happens to the "green" ring? Green ring has to be thinned by lathe and then you could screw in inner part of M42 adapter (also needed to thin with lathe)
you see all stages of the process here http://album.foto.ru:8080/photos/or/41852/347467.jpg
Max you have it mostly right. Blue and green become the new lens mounting surface for the zero-addition EOS bayonet (flangeless).
Paul is correct re: the ring purpose. However it does get shaved down a little but it's not a spacer, it's the actual mount surface (in this new paradigm).
in the 35 1.8 at least (and I think the 21 also) the minolta bayonet is removable, via screws. That allows replacement with an EOS bayonet, after removing the flange. I nest the 2 together and make them one piece, then use original screws/holes in the minolta bayonet to hold it on.
With the 58 1.2 infinity is no problem for me either. the 35 1.8 I havent' gotten quite there yet. good to know it's doable! Now where did I put that epoxy.... ;-)
Now that I have it all open I can see how different this conversion is to the 58.
I have carefully pulled all the rings off like so:
The pasts look different to the Dimka conversion. I guess the trick is to preserve what you can from the aperture ring while removing the old mount and replacing it with the new M42 mount.
Here is a shot of the aperture ring from the front and back. I need to shave off the metal mount and most of the vertical aperture control pin that would connect to the Minolta film bodies?
Max, everything is like i suggest, of course you will preserve original aperture control mechanism. control pin you could completely remove by drilling it off from other side just move other lever and then you see all 4 screws which hold the original minolta bayonet.
This mount is exactly like the 35/1.8 mount, which is great since I know how to convert that no problem.
re: apeture piece - you will end up taking out most of what is in there. As mentioned, take out both arms and all springs to get to screws for bayonet.
Only one of the arms is needed (the one that has a ramp that actuates apeture pin.) The one with the pin that sticks towards the lens mount is not needed at all, and can be removed and replaced with a spacer(washer). use one of the springs in reverse to tension the remaining lever.
Just a heads-up, this is the most complex rokkor conversion I have done (35 1.8, which is the same as the 21 we are talking about here) so it's not for the faint of heart or non-mechanically inclined.
not to scare you off but it's a lot more complex than the 58 1.2. Certainly doable ( I Have done 3 so far) but not trivial.
