3D Print Tolerance & Clearance Calculator

Design mating parts with realistic fit allowances. Includes material behavior, orientation effects, and printer bias compensation for hole and shaft CAD dimensions.

If you already chamfer/compensate first layers, this improves shaft estimate.

Recommended clearances

  • Diametral clearance0.340 mm
  • Radial clearance0.170 mm
  • Expected workable range0.240 to 0.440 mm

CAD dimensions to model

  • Shaft diameter (CAD)19.850 mm
  • Hole diameter (CAD)20.520 mm

These values compensate for typical hole undersize and shaft oversize on typical hobby setup.

Predicted printed results

  • Printed shaft target20.000 mm
  • Printed hole target20.340 mm

What changed this result

  • Material baseline0.200 mm
  • Fit adjustment+0.140 mm
  • Orientation adjustment+0.000 mm
  • Printer profile adjustment+0.000 mm
  • Size adjustment+0.000 mm

How to use this for real parts

Start with the suggested CAD dimensions, then print a quick fit coupon with 3-5 steps around the recommendation (for example in 0.05mm increments). Lock the winning value into your design rules for each material and printer.

Practical rule for moving assemblies

If a part must move freely in all conditions, bias toward sliding or loose fits and prioritize reliable first-layer setup. Tight fits are possible, but only once printer calibration and cooling are consistent.

FAQ

What clearance should I use for 3D printed moving parts?

For most FDM prints, start around 0.2-0.4mm diametral clearance. Tight tuned machines can go lower, but rough setups often need 0.4-0.6mm for reliable motion.

Why are printed holes too small?

FDM holes usually print undersized due to extrusion path geometry and cooling behavior. This calculator adds hole compensation so your final printed hole lands closer to target.

Does orientation change fit?

Yes. Layer direction affects friction, surface quality, and tolerance stack-up. Vertical (Z) motion often needs extra clearance versus XY motion.

Should I design for press fit with printed parts?

Press fits can work for PLA/PETG, but they are sensitive to printer variation. Use test coupons first, then tune interference in small 0.02-0.05mm steps.

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