What fit class should I choose for a bearing?

For standard ball bearings pressed into a 3D printed housing, use FN1 (light press fit). The slight interference ensures the bearing stays in place. For bearings that need to be removable, use LT2 (tight transition).

How do clearance fits differ from press fits?

Clearance fits (RC classes) always have a positive gap between parts — they slide or rotate freely. Press fits (FN classes) have the shaft larger than the hole, requiring force to assemble for a permanent connection.

Why add printer tolerance compensation?

FDM printers have inherent dimensional error (typically 0.05-0.2mm). Holes tend to print smaller and shafts larger. The compensation adjusts both to account for this systematic error.

Do transition fits work well in 3D printing?

Yes, transition fits are actually ideal for many 3D printed assemblies. They allow hand-assembly but hold position well. The slight material flexibility of most 3D print materials helps create a forgiving but secure fit.

3DPrintCalcs

Fit Calculator — Press, Transition & Clearance Fits

Determine press-fit, transition-fit and clearance-fit dimensions for printed parts.

Nominal Diameter

Target diameter for the joint

Printer Tolerance

Fit Class

How We Calculate This

Fit Class Formulas

Hole diameter = Nominal + Fit offset + Printer tolerance
Shaft diameter = Nominal + Fit offset - Printer tolerance
Clearance = Hole diameter - Shaft diameter

The calculator uses simplified ISO fit classes adapted for 3D printing tolerances. RC classes give clearance fits (positive gap), LT classes give transition fits (may have slight gap or interference), and FN classes give interference/press fits.

Frequently Asked Questions

Related Calculators

Scale Calculator

Scale a model up or down and see the resulting dimensions and volume change.

Tolerance Calculator

Calculate clearance tolerances for parts that need to fit together.

Shrinkage Calculator

Compensate for material shrinkage by scaling your model dimensions.

Clearance Calculator

Calculate the gap needed between moving or sliding 3D printed parts.

Wall Gap Calculator

Find the minimum gap between parallel walls that your printer can resolve.

Last updated: February 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.