"Can you print the thread too?" — yes. The question is whether this is the right solution for your part, because there are several ways to hold two plastic parts to each other and they differ in strength, durability and price.
Printed thread: works when large
The FDM printer builds the thread layer by layer like everything else. This means two things:
- Coarse thread comes out fine. A container lid, plastic clamp screw or adjustable foot: coarse-pitch, large-diameter threads print well and last a long time under reasonable load.
- The fine thread suffers. The finer the profile, the more of it is lost in the width of the extrusion line. Small metric threads come out chipped, fused or stripped after a few turns.
Orientation also matters: a thread printed upright (its axis up) is round and true; lying on its side, it suffers like any horizontal hole. And the rule from the tolerances article applies in full force — between the bolt and the nut you need a designed clearance, otherwise they jam.
The metal in the plastic: three working paths
When the joint will be tightened often or bear force, the metal thread beats the printed one:
- Captive nut. The pattern provides a hex pocket into which a standard nut fits snugly; the bolt tightens into it, not into the plastic. Simple, cheap, suitable for repeated disassembly. Our most common tip.
- Self-tapping screw. For a joint that will rarely come apart: the screw cuts its own way into a smaller hole. It withstands a limited number of disassembly cycles, but for a box lid it is sufficient.
- Heat-set threaded insert. Brass threaded bushing that is heated with a soldering iron and pressed into a matching hole. Gives a real metal thread in a plastic part. It requires manual work and an exact hole - if you need such a solution, please describe it in the order note so that we can discuss it in advance.
Joints with no thread at all
- Snap-fit. A tongue that bends and snaps into a groove. Elegant for lids and cases, but the tab is thin and the direction of the layers is critical—the bending should stress the part along the length of the layers, not peel them apart. Here, the material has a say: PETG tolerates bending better than PLA.
- Pin and hole. Two parts are aligned with pins and glued or clamped. Printed pins are good for alignment; for a load-bearing connection, a metal pin or bolt is more secure.
- Gluing. For fixed joints - works great as long as the surfaces are designed with little clearance and enough bonding area.
How to order correctly
If you already have a model with threads and joints - upload it to "Upload model" and write in the note which parts fasten together and how often it will be disassembled. The note travels with the order — and if the geometry looks doomed (too fine a thread, a tongue across the layers), we'll ask you before we print, rather than sending you a part that will break on the second day.
If there is no model yet — describe the task: what needs to be attached to what, is it detachable and what will it carry. Joint design is precisely one of the decisions that is cheaper to make before the first print rather than after the third.