I’m using Mach4 build 4612 with the ESS Ethernet Smoothstepper version 275 and the touchplate attached to this message

I’m using the Touch button with the Z and edge finding X-- and Y-- operations.

In all touch actions the probe finds the surface and retracts with new X, Y and Z coordinates.

For Z when I drive to 0  the tool is exactly on the surface and this makes sense because the Z offset for the touch plate is an input value.

However when I drive the X and Y axis to 0 they are both .5” offset from the workpiece corner.

Where does that .5 come from?   This touch plate has the X and Y touch off surfaces co-planar with the work surface so I would expect that any offset value should be 0.0. The only way I can get a correct X and Y zero location on the workpiece after a touch off it to input -0.5 Work Shift offsets in the fixture table.

So, the key question is why if I have no fixture offsets, my X and Y axis 0 locations after the touch offs are 0.5” incorrect?

Thanks in advance for any help here.

I think I found the issue.  In the Touch documentation it points out that if you use a touch plate for multiple axis the offsets must be the same for each. In my case the Z offset was set to .5, the thickness of my touch plate, but the X & Y touch locations were co-planar with the workpiece so Mach had added that Z offset distant to the X & Y Zero calculations.