That's the point - there is no all-round, which is why it failed. The base metal is only just over-size for the whole job, once the perimeter is roughed the only fixture it has is the middle strut and that only had the tiny tabs or possibly onion skin - just not enough meat.

No offence taken JAZZ, speak your mind ;) There is a long story with these parts, not for here but suffice to say I have customers waiting and really wanted to get them done myself instead of farming them out - this has applied some undue pressure but I think I can win still.

My experience is all manual - I'm used to throwing in a 1/2" cutter, clamping the metal down and diving in at full depth and adjusting the feed to suit as I'm twiddling the handles. The learning curve here is staggering, my presumptions were originally to use a feed and speed guide - set those parameters and have at it - this was wrong by a long-shot and I realise that now. It probably explains why 90% of the videos i have seen on youtube are all running very light cuts.

There is a slim chance that the loss of power on the spindle is connected with my odd VFD issue - maybe it really is a duff VFD after all - the new one should arrive tomorrow and i'll be fitting that before running any more tests - another good thing with a UK supplier is that help is only a call away and they are very helpful ;)

I will get that set up, check my Z axis calibration, then run some simple tests on scrap before diving in again. The new cutters will be here for the weekend and I will switch to a more softly-softly approach to feed rates as it seems most others do.