Parallel ruler with two swinging arms (parallelogram) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/swinging-arm-parallel-ruler-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 325 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Two straight-edges joined by two equal arms pivoted 100 mm apart on each: the four pivots always form a parallelogram, so the upper bar stays parallel to the lower one while it swings sideways and away from it.
- Drawn with the 60 mm catalog links at 60°: the upper bar is offset 30 mm along and 51.96 mm across; the opening ranges from 0 to 60 mm (arms square to the bars).
- Brown's No. 325 — the common drawing-office parallel ruler; the arms must be exactly equal and the pivot spacings identical or the bars twist.
- Parts (each has its own page): parallel-ruler-bar-200-h100, four-bar-links, dowel-pins-metric.
- Brown's movement No. 325 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
bars  2 × 200 × 20 × 5 mm
arms  2 × 60 mm (four-bar link)
pivot spacing  100 mm
opening drawn  51.96 mm (60°)

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. 325: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_325.html

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/swinging-arm-parallel-ruler-mechanism/index.json
API: https://xemstudio.com/api/geometry?object=swinging-arm-parallel-ruler-mechanism