3D Printing Hole Compensation CalculatorHOLE COMPENSATION

1. 1Enter the diameter of the mating part, e.g. a 22 mm bearing OD or a 5 mm shaft.
2. 2Choose the print process and the hole orientation (vertical or horizontal).
3. 3Pick the fit — press, transition, slide or loose; choose “exact size” if you just need an accurate hole.
4. 4Model the hole at the “diameter to draw in CAD”; for horizontal holes, add a teardrop top at the given apex height.
5. 5For critical fits, print a hole test plate (e.g. 0.1 mm steps) and fine-tune from measurements.

Following our hole-tolerance guide: FDM with a 0.4 mm nozzle needs +0.2 mm on vertical holes and +0.3 mm on horizontal holes (or a teardrop), with about 2 mm as the smallest reliable hole; SLA / DLP about +0.1 mm, down to 0.5 mm; SLS / MJF about +0.15 mm, down to 1 mm provided the powder can be cleared. The FDM 0.6 mm values (+0.25 / +0.35 mm, 3 mm minimum) are extrapolated. CAD diameter = nominal + fit clearance + process compensation; the printed hole should end up at nominal + fit clearance.

Diametral clearance (hole − shaft), FDM-based: press −0.05 to 0 mm (−0.025 used) for bearings, magnets and dowels; transition 0 to +0.1 mm (+0.05 used) for removable locating; slide +0.2 to +0.3 mm (+0.25 used) for shafts and sliders; loose +0.4 mm or more for print-in-place hinges. For precise fits start from ISO 286 fits such as H7/g6 or H7/k6 and add the process compensation.

An STL export cuts a circle into n sides for chord deviation δ: n = ⌈π / acos(1 − 2δ/D)⌉, with the sagitta s as the largest gap between flat and circle. For press fits keep s below 20 µm. The top of a horizontal hole is an unsupported arch that sags on FDM; a 45° teardrop puts the apex r·√2 above the centre and prints without supports while the lower arc stays true to size.

D_CAD = D + Δfit + Δprocess
D_print ≈ D + Δfit  (expected printed hole)
n = ⌈π / acos(1 − 2δ / D_CAD)⌉  (STL facets for chord deviation δ)
s = D_CAD / 2 · (1 − cos(π / n))  (sagitta)
D_poly = D_CAD · cos(π / n)  (inscribed circle of the polygon)
Teardrop (45°): apex h = r · √2 above the hole centre

Results are for design reference only; confirm against supplier catalogues and the applicable standards before manufacturing.