Centroid CNC12 lathe tool touch off for boring bars - WTF?

Been struggling to understand how to get boring bar tool length offsets correctly measured in CNC12 lathe. I've been finding this all very frustrating but I think I'm getting there now. I was planning to update from 4.80 to 4.82 but TBH I can't see any suggestion from the release notes that anything has been done that would affect lathe touch off. Besides, I now have a custom PLC on account of my ATC turret, which would further complicate matters.

Instead, I've done some experimentation / learning / calculations to better understand what is going on and I seem to have made some progress.

I started out by setting Xref to zero at the point of touch off of Tool #1, which I'm considering to be my reference tool. I'm not sure why I'd do this from what I've read in the manual but it seemed sort of in line with what Uwe said just now. Subsequently, the offsets are back around the -70mm for the external tools. But I still couldn't understand the boring bar offset.

On my machine, the boring bar tip is ~26.5mm closer to the turret axis (ie in radius units) than the external tools. That's equivalent to a difference of ~53mm in diameter. My probing "tip" is actually a piece of 3/8" square stock (so that I can probe it from all sides unlike a ball tip) ie 9.53mm across flats. The section in the CNC12 lathe manual dealing with boring bar offset measurements says "multiply the [boring bar] manufacturer’s offset by negative two (-2), and type the number into the X Offset field. The value you type should appear as being added to the measured X offset already measured." This seemed to be pretty relevant and indeed my "offset problem" distance is twice the width of the probe tip.

Quite simply, if I subtract twice the width of the probe "tip"(ie a total of 19.06mm) from the offset, I end up with the "correct" offset. By way of a check, when I change tools and approach a fixed DTI, the typical final "error" in the DRO position between my external tools and the the boring bar is 19mm before this correction is implemented.

So (and yes, I'm still new to CNC12 lathe):

• Offsets are measured as diameter units, not radius.
• As suggested by Uwe Mattern on the forum, the Xref should be entered only once. I can't say I'm quite clear how this works yet but it's a start.
• The auto touchoff process doesn't seem to allow for the width of the probe tip when measuring boring bar / internal tools.
• That's likely because the process outlined in the CNC12 lathe manual tells us to manually enter the boring bar offset. This is essentially the same process used for drills and taps but with the offset entered manually.
• The manual covering lathe tool auto touch off is "commendably brief".
• When I auto touch off boring bar tools with my probe, I will need to subtract twice the width of my probe from the measured tool offset.

Phew. Probably quite a simple problem but it took me some head scratching to figure out!