I used my primitive electric drill. Had to do some small guide holes to soften things up, and eventually worked my way up to one almost as big as the tank. Now trying to decide whether to use pitch glue, gorilla glue, or epoxy to hold the whole thing together. Leaning toward gorilla glue, but pitch glue would be more fun if I can figure out how to melt it and get it inside the hole. I'm kind of depending on the glue to hold the teeth in from the inside, too. Maybe if I shoved in a little pitch glue suppository, heated the tang up really good, and put it in to melt the glue??? Maybe.