Crown wheel (face gear), module 1.5, 54 teeth, generated by an 18-tooth spur pinion — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/crown-wheel-m1-5-54t-for-18t-pinion/  (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 89.0, width 89.15, height 9.63
- Face gear: 54 teeth standing on the face of a Ø89 disc (Ø8 bore), from radius 37.5 to 44.5 mm, each tooth the envelope of the module 1.5, 18-tooth involute spur pinion it runs with (the catalog gear, its own root form included): the pinion's axis lies in the wheel's pitch plane, 13.5 mm (its pitch radius) above the tooth-root plane's offset, and the pair turns at 3 : 1 while the pinion's teeth sweep the spaces — computed in 7 planes across the face at 0.25° steps and lofted through them (spline fit within 0.008 mm).
- Tooth top at +1.5 mm above the pitch plane, space bottom at −1.875 mm (0.25 m clearance under the pinion's tip); the toothed band is a 54-gon, so every tooth ends flat at its own inner and outer radius. The tooth form changes across the face: wider and undercut toward the centre, pointed toward the rim — which is why a face gear's face width is short (here 7 mm, from 3 modules inside the nominal pitch radius 40.5 to 4 outside).
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

dimension  value
module  1.5
teeth  54
pinion  18 T spur (catalog gear-m1-5-18t), axis in the pitch plane
face  r 37.5 → 44.5 mm (7 mm)
tooth top / root  +1.5 / −1.875 mm from the pitch plane
disc  Ø89 × 6 under the teeth, Ø8 bore
ratio  3 : 1

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. 26: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_026.html
- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/crown-wheel-spur-pinion-mechanism/

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/crown-wheel-m1-5-54t-for-18t-pinion/index.json
API: https://xemstudio.com/api/geometry?object=crown-wheel-m1-5-54t-for-18t-pinion