~EDIT~

I've been contacted by a fellow Printables member who has rightly pointed out that this model was originally designed by Scott Eliott and is called the "Cast Diamond". The real deal can be purchased here. I value the tinkering aspect of design and 3D printing, and did this as a bit of fun - the work on Tinkercad is entirely mine, but it would be good if others sharing this work could reference the original designer too.

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Chris Ramsay, popular social media magician had a short reel on his Facebook page. I think he posted it a few weeks ago, but I only saw it yesterday.

Anyway, I liked it so I thought I would try to duplicate it in Tinkercad. I surprised myself and was able to get it to work.

I designed it to be quite small - 40mm across - but I think that it could be printed larger. The tolerances are resonably tight, but it goes together without any force or without needing to sand the mating parts.

~EDIT~ It couldn't be printed larger - the clearance worked in some places, but not all. I've now redesigned it at twice the size.

I designed it to be printed upright and it doesn't need supports, but adhesion in this orientation will obviously be an issue - for this reason I added a couple of small supports to the side to keep it steady as it gets taller. These worked, and can be easily trimmed off after. A little light sanding around these areas to tidy up helps the final finish, but it's minimal.

~EDIT~ The first supports didn't do a very good job when enlarged - they left a blemish and didn't provide very good support early in the print. I redesigned these as a .4mm wing on the side - this provides excellent adhesion and is easy to trim off and smooth with a light sand.

~EDIT~ I've uploaded a version without supports

Print two of the same piece and then fit them together as shown here.

Here is the original feed with Chris showing how the metal ones go together (spoiler):
https://www.facebook.com/reel/2908715099429478/?s=1x1

These 3D printed ones have a tighter fit.

Here is the Tinkercad:

https://www.tinkercad.com/things/eYabgxRecXu/edit