Hi Andrei. I got your email & PMs but I'll post everything here as there are probably others who want to know how I cut the collar off the steering column.
Dremel is a brand name of a small high-speed drill.
Dremel's web site There are many different manufacturers of similar drills that will work just as well. Here is a photo of a Dremel brand drill.
The cutting wheel I used has a fiberglass mesh in it so the wheel does not shatter. This cutting wheel is Dremel part 426.
After I removed everything off the steering column, I draped some damp cloths over the gauges and dash to prevent the grinding debris and sparks from getting all over the dash. The metal and cutting wheel debris sticks very well to the damp cloth. I cut a small hole through the cloth for the steering column to poke through.
If your are holding the Dremel drill tool in your right hand, the cutting wheel is turning clockwise. You want to hold the Dremel tool in your left had so the wheel is turning counter-clockwise. This is important. You want to hold the drill so the sparks and cutting debris spin away from you and into the damp cloth.
Please wear some sort of eye protection as some cutting debris will still come back at you.
I cut a slit about half the length of the collar. Then I took a thin chisel and pounded it into the slit until the collar expanded and fell off. The collar cannot be reused. The collars are cheap, less than $20 USd. Some photos of my old collar after I abused it with the Dremel drill and a chisel.
I have actually broken screwdrivers using them as chisels doing this. So if you have to, grind the slit wider if needed to fit your spreading tool of choice. It helps the job go faster if you grind the slit on the collar as far as you can without touching the spring. Don't worry if you grind a small scar on the steering column, there is plenty of steel there. I put a small amount of anti-seize compound on the steering column splines before I installed the new collar so next time the collar will come off much easier.
To install the new collar make sure the ignition switch-lock assembly is as far down the steering column as you can get it. Then you start the 24mm nut by hand. This is tricky as you have to compress the spring a bit to get it started. Tighten the 24mm nut as far as you can. If done right the collar will be seated correctly. Remove the nut and assemble the switches and steering wheel. Then install the 24mm nut again. If the horns work correctly, then you have the collar on correctly. If the collar is
NOT on all the way, the horn contact on the back of the steering wheel will not touch the contact ring on the switch assembly and the steering wheel might feel loose.
I hope this helps.
Brian, 97 Passat TDI