Constant-breadth cam: rounded Reuleaux triangle, breadth 40, Ø5 bore at its centre — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/constant-breadth-cam-s30-r5-bore5/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
Catalog version: 2026-10-20

Overall (mm): length 40.0, width 40.0, height 8.0
- Reuleaux triangle of side 30 (three arcs of R30 about the opposite corners) with every edge offset 5 mm, so the corners are R5 arcs: breadth 40 mm in every direction. Bored Ø5 at its centre: turning there inside a yoke 40 mm wide it always touches both faces and moves the yoke 4.64 mm, three times per turn.
- Corner (vertex arc centres) on a 17.32 mm circle; largest radius 22.32 mm, smallest 17.68 mm.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

dimension  value
breadth  40 mm
Reuleaux side  30 mm
corner radius  5 mm
thickness  8 mm
bore  Ø5 at the centre

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. 276: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_276.html
- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/constant-breadth-cam-yoke-mechanism/

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/constant-breadth-cam-s30-r5-bore5/index.json
API: https://xemstudio.com/api/geometry?object=constant-breadth-cam-s30-r5-bore5