Ackerman Pump Pen, the nib is a Hunt 101.
It gives a very fine line, nice for hatching, but with a little pressure, you can also get a stronger line, and with pressure you can vary them in the same line. You can, of course, change the nib out any time. I know you can get these nibs in most fine art stores, or order various separtae nibs from Ackerman's. I tried writing with it, and that works just fine.
The Ackerman Pump Pen, a wonderful new toy! This is a very versatile pen, and can be fitted with a whole bunch of different art nibs. I bought the Gen 3, and this one has a Hunt 101 nib in it. It is a NOT fussy pen, and is supposed to accept all types of ink, acrylic, gouache, watercolor. Right now I have Noodlers Ink in it, and it works beautifully. I haven't exactly figured out the pump yet, (you can see the little oval pump in the barrel above) but what a fine new toy! Here's a portion of a little piece I played with while watching TV the other night:
And here's the link, if you want to check it out: