Fountain pen enthusiasts seem extraordinarily keen to bring a Dremel to bear on their assorted writing implements. Speaking as someone who would hesitate to bring a Dremel to bear on anything more important than a rusty nail, this terrifies me. But sometimes they have a point (sometimes medium, sometimes broad, occasionally oblique), and this is one instance that I mentioned I'd tell you about.
Take the rotring Artpen. Please, take it... At least that's been my feeling about the things for many years. I've had a couple of them since my school days, but could never really like them. They're a bit stingy about letting any ink out at all, the rotring ink itself is pretty Meh (the only time the black seems truly black is when it's all over your fingers), and the length of the thing is inconvenient and makes the pen unsuitable for anything but arty-farty posturing.
Take one Artpen body, thusly. Wrap some tape around it at the point of cuttage, to give you an outside chance of getting a straight line. If you want to use a converter, make sure you allow enough room for it. (Okay, confession time - I probably cut it a little shorter than advisable, but I so hate that taper I wanted as much of it gone as possible.)
previous experience, I seemed to luck into a cut-off disk that actually wanted to stay in one piece long enough to use it. Amazing.
And that Dremel cut-off disk is still in one piece. Which, frankly, I find a good deal more disturbing than pen surgery...