The Bock tap sizes are #6- m7.9x.06 and the #5 is m6.4x.6 unfortunatly I cant add them to the poll now.
This thread and poll are the result of a different thread asking if anyone offers the dies for the different feed taps.
I ordered the 8.4 x 1 dies because I want a tap and die to form a front section that would allow the wider convertors to pass through. (the 8.4 Id) while using a 10mm x .75 thread on the outside for the cap threads.
Well this is very timely as I am experimenting with my new M10x0.75x3 tap and die set today.
First observation is that this is not the same thread as the Jr Gent or Baron kits.
These kits do use the 8.4x1mm thread for the section and this fits very well, so that's all good.
However...........there is always an however isn't there.
If, as you are saying, you want to use the M10x0.75x3 for the cap thread (ie male on barrel, and the M8.4x1 for the female section thread, then there is a problem.
First off, when you drill the barrel to 7.4mm ("L" drill) and thread it with the M8.4 tap, the section is hard to screw in, 7.5mm would be better.
This will allow the smaller converters (eg those supplied by Bear Tooth woods and perhaps others) to be used (7.38mm max diam) but not the Schmidt ones (7.64mm-supplied with Jr Gent II kits) and not the ones you have (from memory ex IDP and about 7.85mm?)
Edit: I have just made one with a 7.7mm drill ("N") and the Schmidt converter still doesn't fit in and frankly the wall thickness is such that I would be reluctant to sell a pen made like that.
In fact to accommodate those you would have to drill to 7.9 or 8mm, and you would have no wall thickness left.
DAMHIKT! Drilled out to 8mm and even with the threaded collar on, the threaded portion of the barrel broke off.
Stands to reason of course, the theorectial minor diameter for the M10x0.75 is 9.25mm the which leaves 1.25mm total, or 0.6mm wall thickness. Thsi MAY work in metal, but it certainly didn't work for me in PR.