Tolerances and fits: clearances that work
How much clearance to leave between printed parts for a press fit, a slide or a rotation. With concrete values, and why holes come out small.
4 min read
If you drew a 10 mm shaft and a 10 mm hole expecting them to fit, they will not. It is not a precision problem: the plastic shrinks as it cools and the nozzle rounds off inside corners.
| Fit | Clearance | For what |
|---|---|---|
| Press fit | 0.1 – 0.2 mm | Pins, lids that stay shut |
| Sliding | 0.3 – 0.4 mm | Drawers, rails, removable lids |
| Rotating | 0.5 mm | Shafts, hinges, wheels |
Holes always come out small
A vertical hole prints as a polygon of straight segments inscribed in the circle, and the plastic also shrinks inward. A 5 mm hole typically ends up 4.7. If it is critical, draw it 0.2 mm oversize, or print it small and drill it to size.