Spindle repairing

Hi everybody.
We here in russia got used Heyligenstaedt Heynumat 5UK cnc lathe.

After a couple of years of working, there is some noise from spindle.
We diassembled it and were ready to chage the bearings. But we faced one sudden problem.
We cant get to the main bearings cause of strange ring. We cant understand how to diassemble it.
I attached some photos of this ring (marked red).
Ok, on this ring we got two holes. Оne with thread through ring. (marked blue). And another from the opposite side without thread not through. (marked blue in red)
There is no thread if to look in the first hole, but we believe that the ring is mounted on the left thread. So we tried to use Hook Wrench first, but no result.
Then we tried to heat the ring and use wrench. No result.

Next we wanted to make a special ring wrench and use this hole with a thread to try to diassemble the ring. But we still not shure if will make it.

So. I wanted to ask. Can you suggest anything in our case. Spindle specialists, Have you met a spindles with such rings? How to diassemble it?

Thanx in advance.

P.S. Sorry for bad english. ^ ^

ok, we did it. We put an oil preasure about 200 bar in the hole with thread. Have made a special wrench and the ring goes. First time we have seen such technology.

it stuck. will cut of this ring. thanx for help guys. x_X