Spool holder + bearings for Orca v04 and v03

It works for spools with inner diameter of 52mm. Same design as the original Thing (http://www.thingiverse.com/thing:26523) but with two new holes to adjust to the Orca v0.30.

Use M3 bolts to fix it up into the frame. Watch out for your Y-frog assembly, it may get stuck into the screw if the screw's too long.

Use base_v04v03.stl to generate gcode. base.stl is there just so you can use the scad file to modify the model.