Screw-jack screw Tr16×4, 90 mm thread, Ø28 head with tommy-bar holes — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/screw-jack-screw-tr16x4/  (CC BY 4.0)
Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
Catalog version: 2026-10-20

Overall (mm): length 28.0, width 28.0, height 106.0
- Tr16×4 trapezoidal (ISO 2904 basic profile, 30°) screw, 90 mm of thread, with a Ø28 × 16 head cross-drilled Ø6 both ways for a tommy bar.
- Lift per turn = pitch = 4 mm; with friction coefficient 0.15 a 30° Tr thread at this lead angle (4.5°) is self-locking, so the load stays up.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

dimension  value
thread  Tr16×4, single start, right hand
thread length  90 mm
minor Ø (basic)  12 mm
head  Ø28 × 16, 2 × Ø6 cross holes

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
- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/screw-jack-mechanism/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/screw-jack-screw-tr16x4/index.json
API: https://xemstudio.com/api/geometry?object=screw-jack-screw-tr16x4