Parametric ( Ultimachine 1Kg ) spool hub bearing

A bearing hub for my 1Kg spool from ultimachine.

STL spool ID = 51.87mm, SCAD provided to change as needed.

Uses 608 bearing by default

I'm using it with http://www.thingiverse.com/thing:22759 as a bracket

Update: Changed scad to be clearer on variable names. Added 1 layer skin under hole.