Bevel gears, module 1.5, 20 : 40, shafts at 90° — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/bevel-gears-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 25 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Two cone-shaped gears whose pitch cones share an apex roll on each other like friction cones: the shafts meet at the apex at any angle (90° here) and the ratio is the tooth ratio, 40 : 20 = 2 : 1. Equal gears at 90° are mitre gears.
- Pitch cone angles from tan δ₁ = sin Σ / (N₂/N₁ + cos Σ): 26.57° and 63.43°; cone distance 33.54 mm, face 11.2 mm. The teeth are exact spherical involutes, generated on a sphere about the apex, so the mesh is conjugate at every position; drawn turned 4°.
- Brown's No. 25 (bevel gears for shafts at an angle; mitre gears when the two are equal).
- Parts (each has its own page): bevel-gear-m1-5-20t-for-40t-90deg, bevel-gear-m1-5-40t-for-20t-90deg, linear-shafts-h6.
- Brown's movement No. 25 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
module (large end)  1.5
teeth  20 / 40
ratio  2 : 1
shaft angle  90°
pitch cones  26.57° / 63.43°
cone distance  33.54 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. 25: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_025.html

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/bevel-gears-mechanism/index.json
API: https://xemstudio.com/api/geometry?object=bevel-gears-mechanism