Thanks Jazz for the advice.

I set a 19mm sacrificial board on the machine today and on top of that I set a small 200 x 120 x 13mm thick piece of ply

After setting the machine to "HOME, I then, using my procedure above, brought the arm axis's to the centre of my workpeice. Positioned the cutter to the correct marked centre and zero'd X & Y.

Then I brought the head down and jogged until the cutter (A 3mm dia single flute end mill) just touched the surface and zero'd Z

In my V Carve software I set the XY to centre of the work, and the height of the material as 13mm. Reference start for Z axis was top of workpiece at centre.

When I started the machine and set it all in motion the X & Y axis travelled to the exact set point in the middle of my piece as expected, but the Z rapid plunged into that point to the collet nut depth ! (Until I hit the E Stop button)

What did I do wrong? I'm missing something here and feel a little dumb.... Newbie cock up I know... Loooong time since I did this and it's a fun learning curve again