External Links that I have found useful.
Laser alignment guide (Just add Sharks but applicable to most lasers)
0xFred All sorts of good K40 tips
So I bought a cheap Chinese 40W CO2 Laser Cutter and it’s actually OK (Part 3)
Mikes Electric Stuff – Cheap Chinese Laser cutter – A really early K40 blog
40 Watt Chinese CO2 Laser Upgrade with RAMPS & Arudino
Legend of the Cheap Chinese Laser Cutter – Applied Absurdity
My experiences Tales of a Cheap Chinese Laser cutter – Pre-Checks