Press-fit joint

Theory

Press-fit relies on elastic compression of the hole wall and/or the pin. A standard 0.1–0.2 mm interference works for FDM plastics; metal pins into FDM holes need 0.05–0.1 mm because plastic deforms more than metal.

Application

Print the hole 0.1–0.2 mm undersize vs. the pin. Chamfer the hole entry 45° to guide the pin. Apply gentle, even force with a soft mallet or bench vise. For FDM use PETG or ABS for better creep resistance. For metal-to-plastic cold press: 0.05–0.1 mm interference.

Common mistakes

FDM holes printed vertically (Z) are round; horizontal (XY) holes are slightly elliptical: measure actual hole before specifying interference. PLA press-fits creep under sustained load. Over-interference causes delamination along Z. Never hammer directly onto a FDM part: spread the load with a flat pad.

Related terms: Clearance for moving / mating parts, Dimensional tolerance, Heat-set threaded insert