Proto G from instructables asks the question. Have you ever wondered if it was possible to 3D Print a funcational key? Well, it is and he can assure you it works just fine. He says he would not use it as a main key, but it is great to print a few spare keys to your room, office or house. Save your key on a usb stick or cloud drive and print it anywhere!
After only having 1 key to his office he decided to test out a 3D Printed spare key. It works great and he hasn't had it break on him after using it 50+ times. Perfect for a spare key!
Proto G provided a full tutorial at; http://www.instructables.com/id/3D-Print-a-Fully-Functional-Key/