The hard part for me to understand if there is any 'slop' or binding, runout from the router, gantry etc, I should see the same margin of error on the outside of the pocket, not just the 'island'. It doesn't matter what bit size I use, and I can get the same error cutting .020 deep versus .08 deep on a single pass. I'm only cutting acrylic and a .020 deep pass with a brand new bit shouldn't put any strain on the motors, etc to cause this deviation especially when it seems to occur when pocketing.
Hell, I accidentally hit a clamp once and it almost ripped it out of the track. So the system has some torque behind it.
Last night, I ran a test, I cut a .5 circle, no pocketing, just cut it to a depth of .0625. it measured .5007. I then told it to pocket a 1" circle around it and avoid the .5 circle. It created a 1" circle and ground the island to .485. Why can I cut the circle accurately, but not pocket with island avoidance? It's like the system changes the radius and doesn't take in or drops out the additional distance for the bit to leave a .5" circle.
I don't know, that's why I'm posting this stuff here, because I'm a novice at this, I believe I understand how it's supposed to work, but it's beyond me as to why I'm experiencing what I am.