Finally got it aligned !
I was not particularly unhappy with the K40 when it arrived - till I tried to cut wood- my cut times were like 15 ma at 3mm/sec repeated 10 times for 3mm ply. Yikes! not good. Then another poster listed an alignment procedure from
firstname.lastname@example.org - I found the beam fairly centred on the first mirror but way off going to the second. took me half an hour to sort that. Being in ham radio I know the dangers of High Voltage so I turned the machine off between adjustments - I recommend you do the same - takes longer but safety first. Once I got the beam centred to the second mirror I got it to adjust to a single point on the head. I found the trick there was to disregard where on the head aperture the beam hit - just make sure it hits on the same spot in all four corners. THEN adjust the head to centre the beam into the aperture. My mistake before was to try to adjust mirror 2 to get the beam centred on the head - this just threw out the beam adjustments to the corners. Now that I did it the right way I found engraving at 10 ma at 50mm gives me a burn depth of almost 2mm - before that I was just marking the surface of the wood. WOW what a difference, this was using a LO head, 20mm Si mirror in it and 18mm focus lens. I can see upgrading the other two mirrors (Mirror 1 - Fixed and Mirror 2 - traveler) to gold ones will help even more. So thank you Dr. Fawcett - your instructions turned the machine into a work horse for me.