I tested this with my H2D previously. Using precision wall+arachne, without hole/contour compensation enabled. 

My machine has been calibrated with vision encoder.

I tested this previously on my H2D to better understand where dimensional accuracy limits in FDM printing actually come from, using precision wall with the Arachne wall generator enabled and with hole and contour compensation completely disabled. 

Positional accuracy and repeatability:

The machine itself was calibrated using a vision encoder, so positional accuracy and repeatability of the motion system should not be a limiting factor. 

Filament:

I’m printing in Bambu PLA Basic, and since no hole/contour compensation is enabled, the slicer is not applying any intentional dimensional offset. 

I intentionally didn't calibrate the filament because in most common cases, it's not the main factor of tolerance issues.

Testing proper method:

I printed test parts with nominal hole diameters of 2 mm, 3 mm, and 4 mm, and measured them using a Mitutoyo caliper. 

The measured diameters were:

1.85 mm for the 2 mm hole, 

2.88–2.90 mm approx. for the 3 mm hole, 

3.93 mm for the 4 mm hole. 

Does this make sense? I think it does. A systematic dimensional error on the order of ~0.1 mm for internal circular features is well within expectations for FDM and already below one quarter of the configured extrusion line width. This error is not caused by poor calibration or lack of machine precision, but by the effective geometric resolution of the extrusion process and how slicers approximate curved features using discrete toolpaths. However, this tiny error in most cases shouldn't cause tolerance issues.

Testing problematci / classic method:

To reproduce the scenario that users most commonly report as “inaccurate holes,” I repeated the same test using the Classic wall generator, again without precision wall and without any compensation enabled. I

n this case, the measured diameters were:

1.6 mm for the 2 mm hole, 

2.67 mm for the 3 mm hole, 

3.7 mm for the 4 mm hole. 

The resulting 0.3–0.4 mm diameter deviation is again expected and corresponds closely to one to two times the half-line width being effectively consumed by inward perimeter placement. 

Conclusion:

This comparison clearly shows that slicing strategy dominates dimensional accuracy for internal features, while machine precision mainly determines consistency and repeatability. You simply cannot expect a 0.4 mm nozzle to deliver sub-0.1 mm dimensional accuracy or tolerance in an FDM process, because that exceeds the physical resolution of material extrusion. Circular holes merely expose this limitation more clearly than most other geometries, which is why they are often used as a proxy for accuracy even though they are among the most demanding features to print accurately.