Need advice removing rack from rack housing

[Flash]

I am trying to remove the toothed shaft from the housing but am down to the last part, im assuming those little ring-halves need to be rotated or punched out?
I just need to extract the toothed section but am stuck now :(

Any advice is appreciated.

Thanks!

http://img301.imageshack.us/img301/7071/21e30rack1.jpg

http://img301.imageshack.us/img301/8971/21e30rack2.jpg

[xLibelle]

rotated. its not two halves, its one threaded ring with two places cut out for a spanner wrench. I ended up making my own spanner to fit that.
There are a couple weld spots that youll want to file or dremel off before attempting to remove that threaded ring.
Easiest way to get it started rotating is with screwdriver and hammer