This is an even faster and cheaper way I do it when I have the stuff to do so, and the pen looks the same but is just a hair heavier. Charlie had some cigar blanks that were junkers I guess that he sent me, so I stripped the blanks off the tubes. You don't even need a metal lathe..it's aluminum..you just need a collet chuck and if you have one of those carbide chisels like Ken sells, that's a big bonus. You chuck the tranny coupler and spin off the ring. The coupler is then pressed in to the lower tube of the pen just like always..you would normally have the ring to stop you going in too far, in this case, you just stop at the nickel exposed area that you trimmed away. Then you put a small drop of CA on the threads and you screw on the tranny. The upper tube..sand the inside of one end. A bit of CA on the nickel exosed area of the tranny coupler and slide the tube over top. The two tubes become one long tube with the tranny secured inside. The coupler gives strength to the joint of the two tubes.
The nib section, well you can just use the standard cigar nib and coupler, or you can spin off the ring on the coupler and make your own nib. If you use the cigar nib, you will have to spin the pen to that size, and if you use your own nib, you can go a bit smaller if you like.
You glue the blank on the tube of course. At the top end of the pen, you just spin away the blank down to the tube..a mortise that would be...and how far back is up to you..for me it's maybe a 1/4" back from the end is fine. The clip, you have to grind the inside of the clip with a dremel so that it fits tight over the tube. I don't have one in the picture, but you also need to make a retention ring. The clip presses over the tube and the ring follows it up...it's not a press fit when I do it, but it's close, and some epoxy and a clamp is used to glue the clip and ring on the top.
Then you see, you make a knob on top to activate the tranny, using a piece of metal that you knurl, or you can use acrylic to match the pen, whatever. The activater piece of brass..the threaded metal on top was cut off, then pushed up into a hole in the finial and glued in.
Hope that helps a bit.