With the drivers quartered, the long axles have now served their purpose. I started cutting the first one with a jeweller’s saw. An hour and two blades later, I decided to switch to a cut-off disk and the Dremel tool.
I took it slow to avoid melting the spokes or (worse) the axle-wheel joint, and I was very careful around the crankpins as they would have disappeared in a blink. To further protect the spokes, I wrapped each wheel in masking tape; this doesn’t do much in the event of a slip, but serves as an early warning if the tool brushes something it shouldn’t.
I cut the axles as close as I dared to the wheel and then mounted them into a V-slot for final grinding and filing. Again, masking tape helped protect the wheel face from accidental contact.