There are a lot of twisty puzzles and rubik's cubes that you can print out there. Their main problem : the core. It's often either hard to print, or totally absent from the design and you have to buy one. You may also want a replacement core for your rubik's cube.

This is a fully printable and customizable core. You can choose the size of the core as well as the size of the screw holes to fit the screws you already have.

The default settings in the customizer (that you can download as well as an STL directly), is based on the QJ 3x3 candy core for M3 screws. It's however a bit thicker to strengthen it.