need a bar 8 mm outer diameter, minimum 175 mm length. Rotational axis is actually a 30 mm long M5 bolt:

Two kind of clamps are provided: square (max 35 mm height) and circular (max 40 mm dia):

All the hardware needed:

• 8 mm outer diameter rod , min 175 mm length
• 2 M5 X 10 mm bolts, with nuts (to join the main body assembly)
• 1 M5 X 30 mm bolt, with 3 nuts (rotation axis) see sketch above 
• 3 X skate roller bearing (608 size)
• 5 M5 X 10 mm bolts ( to secure the clamp and the main body lower support)

The assembly 3D model STEP file is self explanatory. 

I printed the blades with a 0.25 mm nozzle because they get very narrow at the tops. I recommend the print on the given orientation, no supports needed except for the slots that hold the blades. All part fits a prusa mini. 

important! one of the circular clamp screws moves on the contrary direction, and the reason is they are done by symmetry since I was to lazy on the CAD…