Using the 3-D printer at their suburban public library, they could have just as easily made a pair of ear buds, a citrus reamer, a replacement piece for a broken dishwasher or even the parts for a prosthetic hand.

The tools also make it possible to manufacture parts for a gun, a knife, a sexual object or a copyrighted item. Those kinds of options have prompted debate among librarians over how to respond to the thornier requests for objects the printers could generate.

"It's a really good idea to have those policies in place before you run into problems," said Kate Marek, dean of Dominican University's Graduate School of Library and Information Science.