Hey all, I purchased my 2019 PRO60120 machine (Mach4) used a few years ago and primarily work with 4x8 sheet material. I typically only used the touch probe to set Z0 and manually set X0 and Y0 just by eye-balling it with a 0.25" end mill or v-bit, which was good enough over a 4x8 sheet for the corner accuracy. I figured I would speed up my work flow by using the corner finding feature of the touch probe to find X0, Y0, and Z0 all at the same time. However, when I do so, the bit ends up outside of the 0,0 corner of the stock material, seeming to be at about X-0.125 and Y-0.125. I’m setting the tool diameter to be 0.25" in the touch probe routine and rotate the flutes to face the Y and X direction when prompted to do so. The Touch Plate Dimensions are set to: Touch plate height = 1" and Wall thickness = 0.3125 in the Advanced Settings of the probe routine. Anyone know what the issue might be? Am I assuming correctly that the center of the bit should land at 0,0 after probing?
General info that might help (my dad always taught me to check the obvious things first 
There are two ways to use the touch plate to probe a corner - you hook it over the corner (i.e. measuring the “outside” of a block of wood), or you push it into a corner (i.e. measuring the “inside” of a fixture). The software needs to know which one you’re doing so it can apply the right corrections.
Note: what I ended up doing (linuxcnc) is probing away from the corner when I measure the “outside” so that bumping the touch plate doesn’t push it away from the wood. In your photo, I would probe to the right (X+) and up (Y+).
Either way, you need all the offsets to be correct so it knows the difference between where it touched and where you want the zero to be, for the type of probing you’re doing.
Am I assuming correctly that the center of the bit should land at 0,0 after probing?
That’s correct!
Yes, the extended lip of the touch probe is pointing down and “hooks” on the corner of the material. I probe in the X+ and Y+ directions.
Did you choose the correct corner in the probing routine?
Yes, bottom left
Have to wait till the pros get in 
but those are the correct dimensions on the touch plate.
Is the diameter of the bit set correctly?
Ddi you turn it so that the flutes were at the correct orientation?
Yes to both
If I understand you correctly, having a .25" bit in the spindle, it will overhang .125 in both X and Y as the center axis of your spindle (center of your bit) is at 0,0. When you go to cut something the bit diameter will be accounted for in your design software and eventually the gcode.
Just pay attention to whether you are milling on the line, inside the line, or outside the line. Don’t ask me how I know that.
I know this is obvious, and I’m sure you have it set right, but I use both millimeter and imperial bits. And the other day I was using the touch plate, and I reset the bit to be 1/4 inch bit but forgot to click on the inch radio button, so it thought I had a .25 mm bit.
I was probably describing it incorrectly, but my picture shows where the bit ends up. It’s outside of X0.125 and Y0.125, so probably more like the bit center is at X0.25 and Y0.25. I’m familiar with the on/inside/outside cutting paths in Vectric. This seems to be a probing issue.
Double-checked and I have it set to inches. Thanks for the reminder, because I don’t typically pay attention to that setting.
Would G54 have anything to do with it? I see some custom values set for G54. After reading what G54 does, I believe it gets overridden (or not used) because the probing routine will set the work coordinates for the particular job being run.
I have reproduced this myself 
My issue was that on the touch plate page there was a selection for inside corner/outside corner. I had it selected incorrectly.
I’ll check that setting, thanks!
I just reproduced it in a different way.
I had an angle set in my wcs. I had been poking at the wcs stuff trying to figure out how to use it. I didn’t notice that I had partially succeeded ( a symbol that looks like a > next to the G54 in the main screen)