Craft mithral weapons question...

[Caliban]

No, it's already effectively mw.

Where does it say it's effectively masterwork?

The way I read that passage, it says that it treated as masterwork for creation times only (i.e. instead of using the +9,00 gp price for calculating the creation time, use the +150 gp that a masterwork item would cost.), but it's not actually masterwork. That's why it doesn't affect armor check penalty or give an attack bonus.

But nothing says that you can't also make it actually masterwork. Technically you would have to make it masterwork to be able to enchant it.

 

[(Psi)SeveredHead]

Look at the rules for using Craft skills for making equipment. Do not look at the rules for creating magic items. There are rules for creating masterwork equipment (eg DC 20) and rules for how long it takes to make a non-magical masterwork sword.

A mithral sword is just as magical as a masterwork sword... which is to say there is no magic at all.