Depends on the substance quality. The equation for a hirdsman's sword (copied from
http://ringofbrodgar.com/wiki/Hirdsman%27s_Sword) is this:
Damage = 125*sq.rt.(sq.rt.(player's strength*substance)/10)
As for the Fyrdsman's sword, there is no page for that, so I can't help you there. However, general consensus is that bronze swords are generally stronger than fyrdsman's, and hirdsman's swords are better than bronze.