Elliptical gear, module 1.5, 36 teeth, b/a = 0.75, bore at the centre — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/elliptical-gear-m1-5-36t-centre-bore/  (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 64.18, width 48.97, height 12.0
- Pitch ellipse 61.4 × 46.05 mm (perimeter 36 × π × 1.5) with the Ø8 bore at its centre; teeth generated by a 20° basic rack rolled round the pitch curve (spline outline within 0.008 mm), so it meshes with any module 1.5 involute pinion whose centre is free to follow the curve.
- Turning on its centre, its pitch radius at the mesh swings between the semi-axes twice per turn; the pinion must be free to move in and out to stay in mesh. 12 mm face.
- 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  36
pitch ellipse  61.4 × 46.05 mm
bore  Ø8 at the centre
face  12 mm

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. 35: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_035.html
- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/elliptical-gear-pinion-slotted-bar-mechanism/

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/elliptical-gear-m1-5-36t-centre-bore/index.json
API: https://xemstudio.com/api/geometry?object=elliptical-gear-m1-5-36t-centre-bore