Updated 19 October 2026

FDM hole compensation calculator for pins and press fits

Holes in FDM parts often come out smaller than modelled: the slicer approximates the circle with straight segments, and each layer is squeezed slightly outwards into the hole. How much depends on the printer, the material, the orientation and the diameter, so no single table holds for every part. The reliable way is to print one test hole at the size you need, measure it, and correct the model by the difference.

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Correct the hole

How it is calculated

correction c = modelled test hole - measured test hole hole needed = pin + clearance, or pin - interference model = hole needed + c

• The correction is whatever the test print lost. A positive c means the hole printed small, and the model is opened up by that much.
• The clearance or interference is your design choice. Take it from the fit standard you work to, for example ISO 286 for a bought pin, and confirm it on a printed test.

Getting a good measurement

• Print the test in the same material, layer height and orientation as the real part, and at the same diameter or close to it: the correction changes with the diameter.
• Measure with a gauge pin or the shank of a drill bit. Caliper jaws in a small hole read low.
• A hole whose axis is vertical prints rounder than one lying horizontal, which comes out slightly flattened at the top. A teardrop or diamond top on a horizontal hole prints cleaner.
• A press fit in a thin printed wall can split it along the layers. For a tight, repeatable fit, model the hole slightly small and ream it, or use a heat-set insert.

3Descu publishes no tolerance table, because none has been measured on its own parts. Where a fit is critical, mark it on the order. The design rules explain why.

From the numbers to a part

A corrected model is ready to price. Upload the model and the instant quote returns a price and a delivery date in under a minute, with no account. 3Descu is an ISO 9001:2015 certified factory with 200+ printers, FDM and SLA only. A part that does not match the agreed specification is reprinted or refunded.

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