Horizontal expansion calibration tool

[EDIT] I've uploaded a more recent version here[/EDIT]

In an ideal world, if you print a 10 mm hole and a 10 mm post, the post would fit into the hole. In practise, some inaccuracy is present. In my experience this often shows up as horizontal expansion (HE) of whatever you are printing - a bit of lateral expansion of the plastic during extrusion makes the wall slightly thicker than ideal.

You can correct for this using the "Horizontal Expansion" setting (under "Shell") in Cura. This print