C-mount (1-32 UN): 17.526 mm flange, thread rings; CS-mount — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/c-mount/  (sheet CC BY 4.0)
Basis: Published numbers only (sources per row); thread drawn at the ISO 68-1 basic profile
Catalog version: 2026-10-20

Sizes: see table below
- Flange focal distance is the distance from the mount's reference face to the image plane; adapters and extension tubes must add exactly the difference between two mounts' flange distances to keep infinity focus.
- Machine-vision, CCTV, cine and microscope cameras: 1 in diameter, 32 threads per inch, designated 1-32 UN 2A (ISO 10935, interfacing connection type C). The lens has the male thread.
- CS-mount uses the same thread with a 12.526 mm flange distance: a C lens fits a CS camera with a 5 mm spacer, a CS lens does not focus on a C camera.
- The Unified thread basic profile is the same 60° profile as ISO 68-1, so the same formulas apply with P = 25.4/32 = 0.79375 mm.

parameter  value  from
flange focal distance  17.526 mm (0.6900 in); CS-mount 12.526 mm  ISO 10935 via Wikipedia
throat / inner diameter  not published in a source I could verify (left out)  —
thread  1-32 UN (2A)  standard
major Ø D  25.400 mm  standard
pitch P  0.79375 mm  standard
pitch Ø D2 (basic)  24.884 mm  ISO 68-1 basic profile
minor Ø D1 (basic)  24.541 mm  ISO 68-1 basic profile
files  male and female ring sections, 8 turns, basic profile  —

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia (citing ISO 10935:2009): C mount: 1-32 UN 2A thread, 17.526 mm flange focal distance; CS mount 12.526 mm — web — CC BY-SA 4.0 (text); dimensions are facts — https://en.wikipedia.org/wiki/C_mount
- Wikipedia: Unified Thread Standard (ASME B1.1): same 60° basic profile as ISO 68-1 — web — CC BY-SA 4.0 (text); dimensions are facts — https://en.wikipedia.org/wiki/Unified_Thread_Standard
- Bureau of Indian Standards (via Public.Resource.Org): IS 4218 (Part 1):2001 ISO general purpose metric screw threads, basic profile (identical with ISO 68-1:1998): H = 0.866025404 P, 5H/8 = 0.541265877 P, 3H/8 = 0.324759526 P — web — Public.Resource.Org (public law); dimensions are facts — https://law.resource.org/pub/in/bis/S01/is.4218.1.2001.pdf

Free files (CC BY 4.0, Xem Studio; STEP + STL, 2 parts): https://xemstudio.com/files/hardware/c-mount/index.json
API: https://xemstudio.com/api/geometry?object=c-mount