Homemade burning laser can cut metal – Make your own
Class 4 LASERS are the most powerful and dangerous class of lasers, and they are certainly not toys; the beam will burn flesh and retinas faster than you can realize it, and even diffuse reflections can be very dangerous. (with videos)
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This is just too geek cool. A home made laser that can hack through many things, the possibilities are endless, fun and possibly some what dangerous. Something to shove on the todo list!