Pin hinge (print-in-place)

Two interleaving leaves and a captive pin, printed pre-assembled.

A pin hinge is a knuckle (barrel) hinge whose two leaves interleave along a shared axis, with a captive pin running through every knuckle. The pin has an enlarged cap at each end that’s trapped in a pocket inside the outer knuckles, so it can’t slide out — yet the whole thing prints pre-assembled and articulates with nothing to snap together. The clearances that let it turn are plain geometric offsets; about 0.3 mm is a sound FDM default.

Two parts or three. *Separate* is the default: the pin is its own part, held by a cap at each end that sits in a pocket inside the outer knuckles. It cannot fall out, and if you snap one you can print another. *Captured* grows the pin into leaf A instead — the hinge arrives as two parts, there are no caps or pockets to print, and there is nothing that can work its way loose over time. Reach for captured when the hinge is small, when it will be opened often, or when you simply do not want a third part on the plate.

Match the leaf thickness to the barrel. The barrels rest on the bed and the leaves are centred on the pin axis, so unless a leaf is at least as thick as the barrel is wide it hangs *above* the plate — 2.5 mm up at the default 3 mm leaf on an 8 mm barrel, which leaves a palm-sized area under each leaf printing over nothing. The Properties panel says so when it happens. Raising Thickness to the Barrel Ø drops the leaves flat and costs nothing in how far the hinge folds; leaving it as it is works too, as long as you turn supports on.

1. Open the Generate panel from the left sidebar and choose Pin hinge (under Hinges & joints).
2. The whole hinge drops in as one pre-assembled, editable part. The parameters open in the Properties panel, where you set them.
3. Set each leaf’s length, the hinge length, and the leaf thickness.
4. Set the knuckle count and the pin and knuckle diameters, then pick a fit — or Custom to set the clearance gap yourself.