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M42 screw mount (M42 × 1): 45.46 mm flange, thread rings

What is the M42 screw mount flange focal distance? · Standard part · basis: Published numbers only (sources per row); thread drawn at the ISO 68-1 basic profile

Also called: m42 thread pitch, m42x1 thread, m42 flange distance, praktica screw mount, pentax screw mount, m42 adapter stl

Exact dimensions. True size, with no printing tolerance added.

sizes
8 in table

Notes

  • 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.
  • The lens carries the male M42 × 1 thread; the camera body the female one.
  • Not the same as the T-mount (M42 × 0.75): the two look alike but the pitches differ and they do not screw together.

M42 screw mount (M42 × 1): 45.46 mm flange, thread rings size chart

parametervaluefrom
flange focal distance45.46 mmFlange focal distance table
throat / inner diameternot published in a source I could verify (left out)—
threadM42 × 1standard
major Ø D42.000 mmstandard
pitch P1 mmstandard
pitch Ø D2 (basic)41.350 mmISO 68-1 basic profile
minor Ø D1 (basic)40.917 mmISO 68-1 basic profile
filesmale and female ring sections, 8 turns, basic profile—

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

WikipediaFlange focal distance (table of mounts)webCC BY-SA 4.0 (text); dimensions are facts
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 PwebPublic.Resource.Org (public law); dimensions are facts
ISOISO 68-1:1998 ISO general purpose screw threads — Basic profile — Part 1: Metric screw threadswebPublisher's page; dimensions are facts

Free files

★ Free files 2 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

m42x1-male-ringM42 × 1 lens mount external thread ring section: ISO 68-1 basic profile, major Ø42, pitch Ø41.350, minor Ø40.917, pitch 1; 8 long (8 turns), bore Ø36.917 (wall is a design choice); exact nominal, no toleranceSTEP · STL
m42x1-female-ringM42 × 1 lens mount internal thread ring section: ISO 68-1 basic profile, minor Ø40.917, pitch Ø41.350, major Ø42, pitch 1; 8 long (8 turns), outside Ø46 (design choice); exact nominal, no toleranceSTEP · STL
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Plain text: sheet.txt · JSON: /api/geometry?object=m42-screw-mount

M42 screw mount (M42 × 1): 45.46 mm flange, thread rings, isometric render of a generated part
Render of m42x1-female-ring from the free STEP; not to scale.

Fits with

T-mount (T2): M42 × 0.75 thread, 55 mm flange, thread rings, isometric render of a generated part
T-mount (T2): M42 × 0.75 thread, 55 mm flange, thread rings8 sizes★ 2 files
Canon EF mount: 44 mm flange focal distance3 sizes★ sheet
Nikon F mount: 46.5 mm flange focal distance3 sizes★ sheet
Lens filter threads: M40.5 × 0.5 to M112, pitch table and thread rings, isometric render of a generated part
Lens filter threads: M40.5 × 0.5 to M112, pitch table and thread rings17 sizes★ 28 files

Questions

What thread is M42?

M42 × 1 (42 mm, 1 mm pitch), 45.46 mm flange focal distance.

Does an M42 lens fit a T-mount?

No: T-mount is M42 × 0.75, a different pitch.