Internal (ring) gear, module 1, 60 teeth, Ø80 — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/internal-ring-gear-m1-60t/  (CC BY 4.0)
Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
Catalog version: 2026-10-20

Overall (mm): length 80.0, width 80.0, height 8.0
- Ring gear with 60 internal involute teeth, module 1, 20°: pitch Ø60, roots at Ø62.5 (rp + 1.25 m), tooth tips at Ø58.24 (addendum shortened to 0.88 m, the usual internal-gear correction that keeps the tips clear of the pinion's base-circle interference point); outside Ø80 × 8 with four Ø3.4 holes on a Ø71.25 circle.
- A pinion of N teeth meshes inside at centre distance m(60 − N)/2: 20 T at 20 mm, 30 T at 15 mm, 18 T planets around a 24 T sun at 21 mm.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

dimension  value
module  1
teeth  60 internal
pitch Ø  60 mm
tip Ø (inside)  58.24 mm
root Ø  62.5 mm
outside  Ø80 × 8 mm
holes  4 × Ø3.4 on Ø71.25

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. 34: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_034.html
- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/internal-gear-and-pinion-mechanism/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/internal-ring-gear-m1-60t/index.json
API: https://xemstudio.com/api/geometry?object=internal-ring-gear-m1-60t