Print tolerances and fits

Fits: pick a nominal size and process. Each fit has a typical diametral clearance; the tool gives the sizes to model the hole and peg after allowing for how your printer prints holes small and pegs fat.

Calibrate from a test: print a few pegs and holes of known sizes, measure them, and enter designed vs measured. The average error gives per-side compensation (and, with three or more sizes, an optional scale factor by least squares), translated into Orca/Bambu, Cura, and PrusaSlicer settings.

Clearance test: generates a plate with a row of holes at increasing clearance and a matching peg, as a binary STL or as OpenSCAD with each clearance engraved. Holes are modelled as polygons that circumscribe the true circle, so they are not undersized by faceting.

Inserts, screws, nuts: heat-set insert holes, ISO 273 clearance holes, self-tapping pilot holes, socket-head counterbores, and hex nut traps (across flats and across corners), with an adjustable extra allowance for printing.