Measure the hole at more than one depth. If only its entrance at the build plate is tight, the problem is different from a bore that is undersized all the way through.
Where does the fit fail?
Only near the bottom
Inspect the first-layer edge and compare it with the upper opening. Use the elephant-foot guide if the base is expanded. Global scaling changes the rest of a hole that may already fit.
Along the whole vertical bore
Check the model dimension, export quality, actual mating component and slicer preview. Try a small hole coupon with several deliberately labeled clearances before editing the full part.
A horizontal hole is irregular
Inspect its unsupported upper section and any support contact. An uneven opening needs geometry or orientation work, not simply a bigger nominal diameter.
Prusa’s modeling guide explains that fit depends on geometry, orientation, calibration, settings and material. There is no universal clearance value that fits every assembly.
A useful hole coupon
- Keep the same orientation and nearby wall thickness as the real part.
- Label each modeled size so the successful result is traceable.
- Use the actual pin, screw or shaft for the functional check.
- Preserve the printer, material and profile used for the trial.
When a local correction works, apply it locally and check other mating dimensions. Scaling an entire enclosure to fix one hole also moves its clips, outer walls and screw spacing.
