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.

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...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 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