Cutting Lenses for Waterhouse Stops

Has anyone got a good way to cut lenses for waterhouse stops that they can share?

A circular saw would give a nice, clean cut but the blades all seem to be 3-4mm thick at least and I'm thinking the thinner the better. I'd guess the vibrations could also do some harm to the elements in barrels that don't have ways to unscrew and remove them.

A hand-saw would obviously give a thinner and safer cut, but it seems like it would be tricky to get the cut straight on a shiny, round metal barrel.

Thoughts?

I have always used an ordinary small hacksaw with a completely new blade. Cutting across a round surface is easier than a flat surface. I have protected the sides of where the cut will be with tape. The hacksaw makes such a thin cut that it allows for "rectifying" divergences away from the ideal line. A wider "stiffer" saw (already given up for other purposes!) can be used to enlarge the slit. You will have to remove at least one of the cells to get all the tiny brass dust out afterwards. And for mounting the internal flange for receiving the stops