Z axis error woes

[Swarfing]

Hank you can level your bed all you like but as the table moves it will still go down hill or up?

[HankMcSpank]

Hank you can level your bed all you like but as the table moves it will still go down hill or up?

but all those uphills and downhills were present whilst the cutting tool was levelling the bed.....surely what's important here is the 'tool tip distance' to the machine bed - won't that be uniform after a bed levelling run?