The method used in a factory is a special pipe tool with two pins ground or inset to fit the ring notches and a handle at other end. Much less likely to slip when the piece is an inner ring as the pipe is sized to be constrained by the side walls. Similarly on an outer ring the pipe is just sized to clear the ring internally.
Originally Posted by E. von Hoegh
A spanner wrench is a poor substitute.
Not damaged anything yet with pliers.