T i m wrote:

Is there a gadget out there that would de-burr / put a 45 deg chamfer
on the end of a range of small diameter rods (say 2-10mm dia)?

Yes, an inside-out countersink. They have 5 cutting edges, so that
they run true.

Haven't seen one for sale in years, mine are a mixture of '50s and
pre-war. Dead handy gadgets and I snap them up whenever I see one -
excellent tools when starting with a diestock.