On Welded retention collars:

Generally a bad idea fostered by many who are not IT racing. It weakens the axle and leaves it prone to stresses it does not have when uniformily heat treated (at the factory).

The retention collars don't come off. If one is concerned about the collar staying in place, simply double the collars...one next to another for double the retention.

Removal is relatively simple. Create a "flaw" in the collar with a grinding tool...don't go deep enough to touch the axle...and place a hardened chisel into the flaw and "strike smartly". You can run the cutting wheel diagonally across the surface of the collar.

Good racing.

Bill