So, the brief was for the pen to be relatively simple to make, look attractive, use the same nib unit as a good kit pen, be individual, aim at the US$120/£120 market and use techniques that few other people could duplicate.
I have ended up with this prototype:
And the cap detail:
The blue material is fairly transparent acrylic - too transparent for anything other than a prototype, but is useful for seeing where there are problems. The main shape is machined on my metal lathe. The threads are where another technique comes in. Pens require lots & lots of different fine threads. If you buy a tap/die for each, that's horrendously expensive as they usually have to be made to order, so cutting them on a lathe is what most people do. However twin, triple and quad start threads are VERY difficult even for an experienced machinist (and I am far from one of them), and most threads on this pen are multi start. So I have written a program that generates toolpaths for my CNC engraver - meaning that the only thing I have to do is to enter the correct parameters, and use only one cutter to create all the different internal and external threads on the pen.
The Clip and 'CP' inlay decal at the top of the cap was made by a complex and indirect route. First I machined the flat clip shape in 2 parts using the CNC machine into hard wax. This was 15% bigger than I wanted to allow for shrinkage of the clip in the kiln later. Then the 'CP' engraving was machined 0.25mm into the clip with a 0.2mm diameter cutter. After that I poured silicone rubber over the wax to form a mould with a clip shaped recess. Next task was to push Precious Metal Clay (bronze in this case) into the mould, let it dry, assemble the parts and fire in a kiln at 350C for 30 minutes, cool, cover in charcoal, fire at 820C for 40 minutes. After cooling, the [now completely metal] clip was filed, bent to shape, torch blackened to make the engraving black, and then polished. The 'CP' decal was done in an identical method and fired at the same time as the clip.
After all this, I have a pen that is as close as I could hope to being a workable prototype. Have a few things to improve, but that's the idea of a prototype. Pheww. One final job is to polish the good quality nib, as it isn't good enough yet. Pen weight 23.6grams, Cap weight, 9.3 grams. Cap diameter 16mm, Barrel Diameter 14mm. Length capped 130mm, Length uncapped 125mm, Length posted (cap on top of pen) 167mm.
Production pens will use a different material for the body - less transparent & hopefully a more attractive colour - and have a Sterling Silver clip and decal instead of bronze.
Still astonishes me I started off with an 8" rod of plastic & a small lump of heavy brown clay, and ended up with a pen.
Regards,
Richard.
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Don't sell yourself short, Richard! 
