Bisecting gauge (centre finder with two equal links) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/bisecting-gauge-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 410 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Two cheeks on a cross-bar (one fixed, one sliding and locked by a thumb-screw) are the pivots of two equal links that meet at a pin carrying the marking point: the point is always on the perpendicular bisector of the cheeks, so set the cheeks against the two sides of a bar and drag the gauge along — it scribes the centre line whatever the width.
- Drawn with the cheeks 70 mm apart and the 50 mm catalog links: marker 35.71 mm from the bar's line. Leaving the sliding cheek free and pressed to the work bisects tapered pieces too, as Brown notes.
- Brown's No. 410 (bisecting gauge).
- Parts (each has its own page): gauge-cross-bar-160x12x6, gauge-cheek-12x40x16-ch12x6, four-bar-links, dowel-pins-metric.
- Brown's movement No. 410 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
cheeks  2 × 12 × 40 × 16
links  2 × 50 mm (equal)
cheek spacing drawn  70 mm
marker offset  35.71 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
- 507movements.com: Brown's movement No. 410: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_410.html

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