Setting Z to bottom of stock not to top

CNC Machines Shapeoko
3

Hi Mike thanks for the reply, sorry I am still a bit unclear so if I understand you:

  1. Like this
    image

  2. So the black box is my bit as you described lowered to the spoil then go to CM set zero -> and zero Z

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  1. so this is where I am a bit confused - do I now jog x & y as I would to the top of the material and set them to zero, but what do I do with z (do I do anything or keep it at the zero I did in step 2)

image
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Thanks
Sherpa