Differential screw (fine adjustment) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/differential-screw-mechanism/  (CC BY 4.0)
Basis: Xem Studio drawing; classic mechanism (Brown No. 266)
Catalog version: 2026-10-20

Sizes: see table below
- Two threads of pitch p₁ and p₂ on one screw, each in its own nut, one nut fixed: a turn moves the free nut by p₁ − p₂ (0.25 mm for 1.25 and 1.0 mm), with the strength of coarse threads.
- Same hand on both threads gives the difference; opposite hands give the sum (a turnbuckle).
- Used in micrometer stages and precision adjusters. Brown's movement 266 shows a shaft with two pitches moving a bearing by their difference.
- Parts (each has its own page): differential-screw-m8, threaded-rods-metric, hex-nuts-metric. Brown's movement No. 266 shows it (1868).

parameter  value
pitch p₁  1.25 mm
pitch p₂  1.0 mm
advance / turn  0.25 mm

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

Xem Studio scan: not needed; this is a published standard. The sheet is the geometry.
API: https://xemstudio.com/api/geometry?object=differential-screw-mechanism