Fountain Pen Magic is a site worth reading if you are interested in repairing fountain pens. I have said for a long time, that when you go to repair a pen, its a good idea to try to understand why a pen was made the way it was before you go tinkering with it. Even today, there's a lot of science and engineering built into a pens design.
Amadeus Wolfgang has created a website that will keep the repair geek entertained for hours. Detailed information on each facet of pen design. I don't know how I missed it, but miss it I have. No more! Follow the link above and enjoy!