Watch opening tool

After having a Jeweller severely scratch my watch trying to get the back off for a battery change, I've been quite paranoid about getting the battery done.

It took me a while to figure out that with a 3D printer I can make my own tools, and being plastic, there's no chance of scratching them, so rather than buying a tool to do it myself, I made a quick design in solidworks and tried it out, and success.

So I have two STL files uploaded, they suit my two watches, one being a casio with a 41