What are these?

Originally Posted by miked

My though on using a tumbler is to avoid smacking each one with a hammer, too much work for the return for me. Perhaps a different media would work better, something like heavy bolts and nuts, having sharper edges? Mike

These would work well and are always available, one downside to rough media is faster barrel wear. heavy ball bearings or pinballs would work the best IMO. magnetic media is the real key for easier separation at the end. One thing I can tell you from experience is running a tumbler dry and full of metal is going to be really loud.

a cement mixer is another excellent tool for projects like this.