M42 screw threads - different pitches.

[ameerat42]

Hi Folks.
I was keen to try an old lens from a Fujica on an EOS camera, but when I took off the Fujica M42 adapter to put the EOS one on I found that the threads were not the same pitch.

Thread pitch for EOS-M42 is 32 threads/inch, and for the Fujica-M42 it is 25 threads/inch. They are both of the same diameter (42mm, I guess).

It only went on about a thread or two, so I wasn't going to force it on.

Anybody know about this fact? I have searched on-line but have not found anything on this.
Ta, Am.

[I @ M]

From what I know, the "standard" M42 thread is a 1.0mm pitch and there are other mounts such as the Tamron T2 mount that is a 0.75mm pitch.

There maybe differences in other brand lenses as well. :confused013

Try not to confuse yourself by introducing "threads per inch" into your investigations as they simply won't be accurate on a metric diameter thread. Grab a vernier gauge and a set of metric thread pitch gauges and measure the diameters of the lenses and adaptors and then the pitch of the threads on each to get an accurate picture.

[ameerat42]

Ta, Andrew. I used a "thread chaser" (I think it's called) and laid the differet gauged leaves on the threads until they matched. They were marked in TPI.
However, your info is interesting since:
***1.00mm pitch is equivalent to 25 tpi *** This sounds like the man,
and
0.75mm pitch runs out at approx 34 tpi (close to 32 - the best I could gauge), like the one I've got for the EOS-M42.
Am.
Now all I need to know is where to get an adapter from.

[Kym]

Concur with Andrew ... M42 × 1 mm is 'standard' Pentax/Zeiss/Praktica

[Kym]

This may help... http://www.techdot.eu/index.php/2009/01/24/m42-adaptor-comparison-by-dslr-brand/

[jjphoto]

...and
0.75mm pitch runs out at approx 34 tpi (close to 32 - the best I could gauge), like the one I've got for the EOS-M42.
...

What you've got on the Canon body is a T mount adapter, not M42.
T Mount = m42 x 0.75
M42 = m42 x 1.0

JJ

[wheellathe]

If you dont own a thread gauge. take your lens to a bolt supply shop they will almost always measure it for nothing.

[ameerat42]

Thanks to everyone. I tried to answer you yesterday, Kym, but AP went down.
I wasn't sure of what I was expecting to find when I asked this yesterday, but then in the meantime I actually went back and read the article from Wiki (http://en.wikipedia.org/wiki/M42_lens_mount) which explains the diff.
Thanks. It is clear now: there's T2 and M42.
Am.

[Tengu]

I have a European motorcycle and it has some specific bolts with a .75 pitch threads...
I cant find them anywhere in Australia