Yup, I trim the flanges off like that to fit my Adapt-A-Roll, but some cameras are tighter and need a bit trimmed off the ends to fit properly. That's where the lathe would come in handy - you could trim both the length and the girth at the same time and do several rolls in a batch. Then you could insert some short lengths of tubing in the ends to suit the 620 'nub'.

Of course, this only matters for those cameras that you don't want to convert to use 120 directly.