Spur gear, module 1, 19 T, profile shift +0.54, Ø6 bore (meshes a 30 T at 25 mm) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/spur-gear-m1-19t-x054-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 21.95, width 22.03, height 8.0
- Module 1, 20° involute, 19 teeth with a positive profile shift of 0.54 m: its teeth are thicker on the reference circle and the tip is at Ø22.07 so that it meshes with an unshifted 30-tooth gear at exactly 25 mm (the centre distance of a 20 : 30 pair) with no backlash — the 'wrong' tooth count at the right centres, Ferguson's trick. 8 mm face, 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  19
profile shift  +0.54 m
tip Ø  22.07 mm
centre distance with 30 T  25 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-m1-19t-x054-b6/index.json
API: https://xemstudio.com/api/geometry?object=spur-gear-m1-19t-x054-b6