Screw jack, Tr16×4 (4 mm lift per turn) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/screw-jack-mechanism/  (CC BY 4.0)
Basis: Xem Studio design following Brown No. 389 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Turning the screw in its threaded body lifts it one pitch per turn (4 mm). Ideal force gain = 2π × lever radius / pitch: 2π × 40 / 4 ≈ 63 with the 80 mm tommy bar; friction in the 30° thread takes about two-thirds of that and keeps the load from running back.
- Basic-profile Tr16×4 trapezoidal thread on screw and body, drawn engaged with no allowance.
- Brown's No. 389 (lifting jack).
- Parts (each has its own page): screw-jack-screw-tr16x4, screw-jack-body-tr16x4, tommy-bar-6x80.
- Brown's movement No. 389 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
thread  Tr16×4
lift per turn  4 mm
lever radius  40 mm
ideal gain  ≈ 63

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Henry T. Brown (1868, public domain): Five Hundred and Seven Mechanical Movements — scan on archive.org — web — Publisher's page; dimensions are facts — https://archive.org/details/fivehundredseven00browiala
- 507movements.com: Brown's movement No. 389: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_389.html

Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/screw-jack-mechanism/index.json
API: https://xemstudio.com/api/geometry?object=screw-jack-mechanism