C/Y Sonnar 135mm f/2.8 MM conversion, part 1 - removing the original mount
This is a brief guide to converting the C/Y-mount Carl Zeiss T* Sonnar 135mm f/2.8 MM lens to another mount for use on a DSLR. (Note that Canon EOS and four-thirds users can probably adapt the C/Y mount directly with an adapter, but that's not possible for Sony, Pentax, or Nikon DSLRs due to register distance.)
This guide focuses on the preparation of the lens for installation of the replacement mount. Obtaining a suitable replacement mount is left as an exercise for the reader. =)
(One good and cheap source of replacement mounts are flanged M42 adapters; ignore the M42 part and you've got a thin, flat ring with a mount compatible with your DSLR on one side.)
Read through the entire guide before beginning! And note that this guide is just based on my personal experience with this one copy of one version of this lens. There are different versions in C/Y mount, and the process other versions may or may not be similar!
Removing the original mount
To start the conversion, the original mount and aperture ring must be removed. The mount on the MM version of this lens (pictured) is attached with four screws. There AE version of this lens does not seem to have these screws, and I don't know how to disassemble that one (never seen it except in pictures).
Note that the screws are glued in, so use a quality screwdriver of the correct size and apply pressure when turning.
See the first comment below for additional tips. (This guide is continued in the next photo.)