Screw-Through Fir Tree

The model

The tree consists of two parts with four spiral walls each, about 3.2 mm thick, which lie inside each other like two snail shells. Part A carries the core with the tab for the star, part B stands on a ribbed foot ring. On the cone surface the walls of both parts alternate, which creates the diagonal stripes.

Both parts are twisted evenly over the whole height (150° over 105 mm, pitch 252 mm per turn). So every wall stays in its own lane while screwing: part B runs completely out of part A downwards. If you pull off the plugged-in star, it also passes completely through upwards; with the star it is 9.5 mm upwards. The gap between the walls is 0.53 mm by calculation and at least 0.48 mm in the triangle mesh of the files; in 48 screw positions over 235 mm of travel the parts do not touch.

A and B are printed separately, each standing on its base and in its own color, the star lying down. A further file has both parts already nested (single color, in one print). The fit test is a 41 mm high section with the same wall thicknesses and the same gap, to check your own printer in advance. The pictures show red/white and turquoise/gold, each with a golden star.

View print notes (German)

Print notes included in German; part names are self-explanatory.