Round vector pathing issues

I know there have already been a few threads about this, but I’m adding another in hopes that Onefinity will take a closer look. I’m having persistent problems with round pocket accuracy, and at this point I’m fairly certain it’s not a toolpath or setup issue.

The issue:
I was cutting a simple challenge coin pocket today—a 0.75" diameter round pocket at 0.15" depth. No matter what I do, the pocket consistently comes out undersized.

I’ve tested just about every variable I can think of, including:

  • Climb vs. conventional cutting

  • Offset vs. raster pocketing

  • Multiple passes and varied cutting strategies

I’m roughing with a 0.25" end mill, and the result is always the same. The coin only fits if I draw the pocket as 0.91" instead of 0.75", which obviously shouldn’t be necessary.

At this point, nothing I change in the toolpaths makes any difference. This feels like a systemic round-pocket accuracy issue, not a CAM strategy problem.

For clarification, I have:

  • Measured the bit diameter with a micrometer

  • Verified the correct bit diameter in the software/tool database

  • Confirmed it’s a pocket toolpath (so no “inside/outside vector” confusion)

  • A consistent maintenance routine as recommended by Onefinity

  • Never needed to tram the machine before

  • Never calibrated X/Y via MDI (didn’t know that was a thing)

  • Not calibrated X/Y in general

  • Noticed this issue starting around June after a firmware update (approx. two updates ago)

Is anyone else seeing this behavior, or can Onefinity explain what might be causing such a large dimensional error?

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That’s weird, are linear movements accurate? For example will G91 G0 X6 move the machine in +x by exactly 6 inches? The same in Y?