To be honest? Google a weapon list >.> Theres not that many. If you're 20 hours in, you might be able to get the majority, or you may be able to get none. What bosses have you slain?
I just took a look at them and my Saw Cleaver is already upgraded to around 140 damage, which is far better than any other weapon's base damage output. So what's the point in getting them?