I tried to print a tool to remove the gear on a motor shaft (remembering to have seen one but can't find it again)...

But that didn't work (contrary to hammering it with an M4 screw while safely holded in a vice).

[edit 05/11/2012] Just use a vice : youtu.be/pT2zk--KqBo

[edit 01/06/2012]
Now may work :)