Inserting steel dowel pin into hole with interference fit I'm building a product which requires a dowel pin inserted into a plastic piece. I'm planning to 3D print the plastic piece with nylon (must be nylon for biocompatibility), but the tolerances won't be sufficient to ensure a consistent press-fit for the pin. To get around this, I plan to undersize the hole, and then ream it out with a reamer on the drill press. There will be 1000 pieces on this run. Any flaws you can see with this design?

It is not possible to insert a steel dowel into a hole of a plastic workpiece with a press fit: at least not for long. Tremendous force is exerted on the plastic by the steel, and the plastic will soon begin to deform in a process called cold flow or creep.