BatchPCB mentions minimum drill of .5mm (not minimum hole) but Eagle kicked
off my design with .3048mm vias. Of course, vias are drilled 
Wondering if .5mm refers to plated thru-holes, and not drills? In which case I’m
fine with .3mm vias, I’d presume? Gold Phoenix mentions these numbers on their
specs, which I presume apply to vias;
DRILLED HOLE DIAMETER (MIN) 0.1mm
FINISHED HOLE DIAMETER (MIN) 0.075mm
Any hints on suggested via diameters?
On http://batchpcb.com/index.php/Faq it says 20mil (~0.5 mm) minimum drill size. 20 mil is actually .508 mm. As I understand it, that refers to the hole size after plating. The drill to achieve that is larger, but you don’t need to think about that.
The 4-layer boards say “13mil (~0.33 mm) minimum drill size” if you really need smaller vias from BatchPCB.
That is the way I read it.
Yes. Most board houses quote finished hole sizes. I’ve heard that Olimex does not, but I don’t live in Europe. In the Eagle DRC, just set the minimum drill to 20mil and leave it be. I tend to make all my vias 20mil.
A plating allowance must be made when using Olimex, it caught me out once.