I recently made a small CNC machine and have been looking for ideas to start dabbling with milling copper. This might be the idea I was looking for...thanks. would probably so it out of copper sheet rather than pipe though. I've got some 1mm sheet already.
Folks are making opinel higonokami hybrid knives with mixed results, copper pipe seems to be the trick.
Tempted but reckon it'll be a very crude attempt at best.
Edit: all the images from the Opinel Mods fb group.