The main body of the box is my first attempt at a segmented turning with black veneer between the mahogany segments. The base and the top rings are ebony, which were CNC milled. The leaflets are brass, and are guided and held in place by stainless steel pins. Edit: I’ve uploaded the SolidWorks CAD / HSM Express CAM files, STLs, and DXFs to my website: http://dropr.com/premmidha
Originally, I made this with a walnut base, but after seeing the materials together, it didn’t feel cohesive…
…so I parted off the walnut on the lathe and CNC milled an ebony base…
Ebony Base Attached
…and glued it to the walls of the box.
I couldn’t find any instructions on how to design the iris mechanism, so it took some trial and error in SolidWorks…
3D Printed Prototype
…and on the 3D printer…
Solidworks Leaflet Pattern
I eventually came to a design that worked smoothly, though if I had to do it again, I would slightly adjust the arc of the slot. You can grab the CAD files on the link in the first photo in this series.
After machining the leaflets out of ultra-machinable 360 brass stock (McMaster-Carr), I sanded everything and polished the brass with a solvent-based brass polish cream. All CNC tool paths were created in HSM Express. All CNC milled parts were done with a 1/16″ Three Flute TiCN-Coated Carbide End Mill.
There are two sets of pins (made from one set of pins) on the bottom of the iris mechanism. One set has heads, which travel through the slots in the bottom ebony ring. These go through the holes in the brass leaflets and the tops of these pins are fixed to the top ebony ring. The pins were 0.067″ diameter precision perforator pins from McMaster-Carr.
More Guide Pins
The other set of pins are short and ride in the slot on the bottom of the leaflets.
Iris Mechanism Assembly (Bottom)
When the top ring is twisted, the leaflets are rotated around the center of the ring via the long pins…
Iris Mechanism Assembly (top)
…and around their individual pivots by the short pins.
Pre-Finish Final Assembly
The iris assembly was glued very carefully to the box so as not to obstruct the motion of the sliding pins.
Danish Oil Finish
The box was finished with a light coat of Danish oil.
Velvet covered foam insert
I bought some foam and velvet to create the insert which holds the ring. I cut a slot in the top of the foam and spray glued the velvet to the foam. The glue will soak through the fabric, so I only glued the sides so the top wasn’t crusty.
“Wait is this for real?” And then “I think I’m gonna throw up.” And then “Yes!” And then she couldn’t stop burping. #romance
The author of this article is reddit user, premmidha.