Not always it works. 120 spool has not only larger diameter, it has also ticker walls, they need to be sanded down. This requires sealing the edges if fillm to prevent any dust to get between spool wall and film. In many old 620 cameras the width of the spool chamber is too small to take 120 in their original lenght, not only diameter of side walls.120 film spools can be trimmed to fit 620 cameras without re-spooling.
See:
Im new to this and have a kodak vigilant six-20 | Page 2 | Photography Forum
I use a pair of nippers to trim the spool flanges and a rotary tool to sand them down.
Noo problemo. I am not advising you, just pointing things to OP. And then your way is somewhat better in case no 620 spools. :=))How about you do it your way and I'll do it mine?
Goes without saying, guard those old spools carefully, expect they are available somewhere but...
Gotta love those oldies.