20 years ago when I was a proper illustrator, I used to work chiefly with Rotring Isograph pens. These days I'm a bit more relaxed, and use a lot of pigment liners, because the ink dries so much more quickly, and I don't end up with ink stained fingers. However, the bolder lines with the fibre tip pens aren't as pleasing, so I used my trusty old 0.5mm isograph for the outlining of the pirate robots I've been drawing. 0.5mm isn't really thick enough, so I have had a rifle through my drawer this morning, and found the components of half a dozen old isographs, including a 1.0mm nib.
There's something comforting about disassembling an isograph pen, cleaning the bits and putting it back together... maybe it's because it was a displacement activity from olden days, maybe because it's good to see the pens have lasted 20 years. Whatever, I'll soon have a chunky line isograph up and ready... trouble is I seem to remember it never worked very well, which is why I put it aside all those years ago.