For once, I have NO real or serious answers for you. I'm looking forward to what others with experience have to say about it.
My only thought about the pattern problem is to use carbon paper and trace the pattern directly onto the metal surface. Or sandwich the metal between two pieces of wood which would probably be a waste of materials in both metal and wood.
As for sharp edges my only idea is to sand or file the edges by hand and forget any powered tools on such a small piece. If you use REALLY fine sandpaper (like 800 grit) you may be able to remove fine scratches with metal polish (or even toothpaste) but, it is still a lot of hand work.
A rock tumbler is out of the realm of my knowledge. I know what they are and have seen them used but mostly for larger more durable parts and materials.
As for making necklaces (which would be my first plan for them) it really depends on the shape and size of the cutting. Either would work well, it is just a personal choice.
I saw your pieces in the "Brag" section and really like them. Good job! You have inspired me to try some as I have three grand daughters.
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Now for my questions.....How thick of material do you use and what blades? I assume you use metal cutting blades but, who knows?
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Rog