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0008: A hanging-ornament variant of every piece

Date: 2026-10-03. Status: accepted by the owner.

Context

The objects make natural tree ornaments. A thread hole near a spike tip turns any piece into one, with no hardware. Drilling such a hole by hand into a finished print is awkward and risks cracking a spike.

Decision

  1. A third set of files for every printable piece: cut halves with a 1.5 mm thread hole, at both sizes, alongside the whole and plain cut STLs (hangers.py, meshes.export_ornament). Printables listings carry all three.
  2. The hole runs along the approved cut plane's normal. It is vertical in print pose, so it needs no bridging or support.
  3. The spike is the most prominent one the cut plane bisects, so the hole passes through both halves and aligns on gluing. When no spike lies in the plane (the irregular pieces), the hole goes through the most prominent spike within 35° of it, entirely within one half.
  4. The hole starts 9 mm from the tip (the owner asked for 8–10 mm). It moves inward in 0.5 mm steps until at least 1 mm of wall remains on both sides, and it fails above 16 mm. The final distance and wall are recorded per piece and size in catalog/exports.json.
  5. Safety checks. The volume removed must match the cylinder crossing the spike, so a bore that cuts into another part of the object fails the export. Booleans and the split use manifold3d, and every half must be watertight.
  6. Ornament halves are always two files (a and b). The hole breaks the symmetry that made the plain halves identical.

Reopen if

A printed ornament shows a better diameter, distance or thread path: for example, a hole perpendicular to the spike within the cut plane, if vertical holes clog with glue.

Amendment (2026-10-03)

The minimum side wall is raised from 1 mm to 1.5 mm (hangers.MIN_WALL_MM), at the owner's request. A 1.0 mm wall is about two perimeters of a 0.4 mm nozzle, which is fragile for a piece hanging from a thread. Holes on thin spikes now sit further from the tip. Each piece's final distance and wall are recorded in catalog/exports.json.

Verified (2026-10-03)

On the owner's prints (settings on the printing page), the 1.5 mm hole needs cleaning up with a 1.5 mm drill bit in a pin vise. After that it suits a monofilament loop. The diameter stays at 1.5 mm.