An assembly method where a component is forced into a hole with slight interference, creating a permanent friction joint without fasteners.
Press fits rely on elastic/plastic deformation creating hoop stress in the hole and axial stress in the shaft. For thermoplastics, ultrasonic or thermal insertion melts the host material locally, flowing it around knurls. ISO H7/p6 to H7/s6 define press fit grades for metals.
Brass heat-set inserts (M2–M8) are the standard for FDM printed enclosures and mechanisms. Recommended hole diameter = insert OD − 0.2 mm. Insert with a temperature-controlled soldering iron at 200–230°C for most thermoplastics. Pull-out strength typically 3–10× bare thread in plastic.
Inserting too fast tears the surrounding plastic. Too slow lets the insert cool and seize before seating flush. Avoid press fits near thin walls (< 2 mm) or unsupported bridges: the hoop stress can crack the part.
Related terms: Interference Fit, Assembly Clearance, Thread (3D Printed)
| Field | engineering |
|---|---|
| Also called | force fit, knurled insert, thermal insert |
| Source | EDi Brain: rules-core |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert