Today a little brass rod I ordered arrived,
It was for the trunion bolt, (I might get some hex for that) and the crank pin.
I started on the crank pin and I would've got it finished, but the god old tap and die set let me down once again. Before I threw it all half way across the UK I stopped, and put the small useless tools in the bin where they belong! I had some success with using the bigger sizes of that set, M8 and M6 etc.. But the smaller ones are not machined properly, if at all.
Anyway... Onto the crank pin.
I started by facing the brass then turning the diameter to 3.5 mm. From there I worked my Down with small cuts until the hole in the Conrod of the piston was a good fit, not sloppy but enough play so it just "dangles"
Facing:

Testing with the piston:

I then proceeded to take part of the pin down to 3mm so it can be threaded with the die.

I got the die out and it wouldn't start on the pin. The exact problem I was hiving with the taps, I applied a bit more pressure while turning. And then the die just slipped off the end leaving a nice trail of marks behind it.

Being the perfectionist that I am, tided up the end and extended the 3mm diameter a little bit. I'll get a 3mm die from a good tool shop next to my college and thread it on Thursday.