I have almost 3000 grinders... Is there anything I can do with them?

I'm going to assume that you are mostly on 13*+ Weapons, right?

In general it is a good idea to keep a stack or two of Grinders for things like enhancing Units, Rings, and 12*-and-lower fodder weapons, but other than that, you can just NPC them for ~300k a stack.

Yeah 13 star and up so I use Lambda's and my normal Grinders are just kinda sitting there. Thanks for that.