How about one of these Dean is bound to be impressed https://www.youtube.com/watch?v=KcHUKqY422M#t=78
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How about one of these Dean is bound to be impressed https://www.youtube.com/watch?v=KcHUKqY422M#t=78
There are manual versions around which use something like a modified power drill to provide the punching action, dangling from a counter-balanced wire to take the weight, so you can build designs freehand. I had to to a bit of maintenance on the punching mechanism for a friend once. Never thought of a CNC conversion, though!