Erik,
I agree with RobS. I would just hold off on everything for right now. A couple of words sources of supply.
If you go with Richard's first project, the clipless fountain pen using taps and dies:
El Grande grip section and nib is available from
Pen Kit Making Supplies Berea HardWoods
The El Grande section will require an M10-1 tap
Richard's book will give you several ideas for barrel to section threads. I used 1/2x32, but there are numerous possibilities. You will need both the tap and die. Get 1" high speed steel round dies. A plug tap will be sufficient.
You will need a die holder and a tap guide.
If you choose to make threaded mandrels (see below) you will also need an M10-1 die.
All of this tooling is available at a reasonable price from
Victor Machinery - Metalworking tools and supplies. Try to order it all at once as they have a $25 minimum order.
All of the tooling recommendations assume that you have a 1/2 inch jacobs style chuck for your tailstock.
Richard will tell you to make two threaded mandrels from steel to hold the barrel and cap while you shape them. Some of the folks here use pin chucks quite successfully. I have always made threaded mandrels from aluminum or brass (which you can do on a wood lathe). Your choice.
Means of precision measurement (Harbor Freight or Lowes digital Caliper) is a necessity.
Workholding:
Depending upon what you already have, you may not need to spring for a collet chuck yet. That said, I would tend to go along with RobS and hold out for the Beall. The main reason from my point of view is that the PSI appears to rely strictly on hand strength for tightening, and sometimes that just isn't enough.
This is probably more than you wanted to know, but hope it was helpful.
Bill