FDM fit and clearance calculator
Find a useful starting size for a printed hole or pocket. The calculator uses total diametral clearance, so the number it returns can go straight into CAD.
Set the mating part
Enter the measured shaft, insert or component diameter. The result is the hole or pocket size to draw in CAD.
Draw the hole at
8.35 mm
Moves freely without being deliberately loose.
- Measured part
- 8.0 mm
- Total diametral clearance
- 0.35 mm
- Clearance per side
- 0.17 mm
How to use the result
Measure the real mating part with calipers, select the movement you need, then draw the returned diameter. For a slot or rectangular pocket, apply the same total clearance to each overall dimension.
A small fit coupon is still the quickest answer when the feature matters. Print several nearby sizes on one plate, test them against the real component, and carry the winning size into the final model.
What changes the fit
- Holes usually print slightly small while posts print slightly large.
- ABS and ASA generally need more room because cooling shrinkage is greater.
- First-layer bulge can spoil an otherwise correct fit; a short lead-in chamfer helps.
- Printer calibration, orientation and material batch all move the final dimension.
Need the fit checked on a real part?
Send the model and the critical measurement. We can quote a test coupon before the full print when the fit matters.