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Bisecting gauge (centre finder with two equal links)

How does a bisecting gauge find the middle? · Hardware · basis: Xem Studio design following Brown No. 410 (1868)

Also called: bisecting gauge, centre finder, center finding gauge, centering gauge, gramil de centrar, Mittenanreißer

Exact dimensions. True size, with no printing tolerance added.

sizes
4 in table

Notes

  • 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.

Bisecting gauge size chart

parametervalue
cheeks2 × 12 × 40 × 16
links2 × 50 mm (equal)
cheek spacing drawn70 mm
marker offset35.71 mm

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Henry T. Brown (1868, public domain)Five Hundred and Seven Mechanical Movements — scan on archive.orgwebPublisher's page; dimensions are facts
507movements.comBrown's movement No. 410: figure, his text and an animationwebPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Xem Studio design: free to use, print and sell things from; not to be republished as files. Xem Studio Design License. index.json

bisecting-gauge-mechanism-assemblyAssembled mechanism, all parts placed at one pose (STEP keeps each part separate)STEP · STL
Let your AI pull this. Add https://xemstudio.com/mcp to Claude, ChatGPT, Cursor or any MCP client (free, no account, one minute) and it can look up exact sizes, mating fits and free STEP/STL from every chat.
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Plain text: sheet.txt · JSON: /api/geometry?object=bisecting-gauge-mechanism

Bisecting gauge (centre finder with two equal links), isometric render of a generated part
Render of bisecting-gauge-mechanism-assembly from the free STEP; not to scale.

Fits with

Gauge cross-bar 160 × 12 × 6, isometric render of a generated part
Gauge cross-bar 160 × 12 × 6160.0×12.0×6.0 mm★ 1 file
Gauge cheek 12 × 40 × 16 with a 12 × 6 channel for the bar and Ø3 link pivot, isometric render of a generated part
Gauge cheek 12 × 40 × 16 with a 12 × 6 channel for the bar and Ø3 link pivot12.0×40.0×16.0 mm★ 1 file
Four-bar links: flat links with 20 to 100 mm hole centres, isometric render of a generated part
Four-bar links: flat links with 20 to 100 mm hole centres7 sizes★ 7 files
Dowel pins, 2–6 mm (ISO 2338 / DIN 6325), isometric render of a generated part
Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)5 sizes★ 23 files

Questions

How does a bisecting gauge find the middle?

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.