Spur gear, module 1, 30 T, 26 mm face (thick idler), Ø6 bore, tips at Ø31.5 — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/spur-gear-m1-30t-w26-b6/  (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 31.48, width 31.41, height 26.0
- Module 1, 20° involute, 30 teeth, pitch Ø30, 26 mm face: wide enough to mesh at once with three 8 mm gears stacked on one pin (Ferguson's paradox). Tips shortened to Ø31.5 (addendum 0.75 m) so they clear the base circle of the 21-tooth wheel with negative shift; Ø6 bore.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

dimension  value
module  1
teeth  30
face  26 mm
tip Ø  31.5 mm
root Ø  27.5 mm
bore  Ø6

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. 504: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_504.html
- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/fergusons-paradox-mechanism/

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/spur-gear-m1-30t-w26-b6/index.json
API: https://xemstudio.com/api/geometry?object=spur-gear-m1-30t-w26-b6