FDM hole correction — FDM printers consistently produce holes smaller than the CAD dimension due to extrusion width, thermal expansion, and perimeter overlap. The correction values used here (PLA/PETG +0.20 mm, ABS +0.30 mm, ASA +0.25 mm, Nylon +0.25 mm, TPU +0.15 mm diametral) are conservative averages across common desktop printers. Your printer may differ by ±0.05–0.10 mm — calibrate with a test coupon for critical fits.
Fit clearances — Values are specific to FDM 3D printing, not machining tolerances. Standard ISO 286 fits are far too tight for FDM. The clearances here (0.00–0.80 mm diametral) reflect what reliably works across typical desktop printers printing in the stated materials. Use the Filament Estimator to cross-check weight before you print.