homing z-axis

[wadero]

Hi, I made my own mill out of an old electronic components stuffer.
All my home positions are at minimum, x y and z, but I noticed that the software on the market assumes 0 position for the z-axis is on the table, so maximum position...if I got it wright.
So I wonder how on earth it 's possible to home this because with different tools there are different home positions, so switches cannot be used.
Can anyone explain how?

[svenakela]

All tool setup's have their own config. A longer mill, for example, has a compensation in Z from your defined Z-zero.