Thread size & pitch of pre-war Bessa 6x9 RF (w/ Skopar)

[Loris Medici]

Hi all,

What is the exact size (and pitch) of the threads in front of the Skopar lens of pre-war Bessa 6x9 RF?

TIA,
Loris.

 

[Jojje]

If nobody has a correct answer you may have to use a thread pitch gauge to find out. (Maybe borrow from a machine shop..)
These inside threads can be tricky to measure.
(I once machined with trial-and-error method a metal lens hood to my Mamiya-Sekor (1959) with a lathe and had to make a tool for it. If my memory serves me right this M40.5 thread had a pitch of 0.75mm and had an angle of 50 degrees.)
Have a look at these: http://www.gewinde-normen.de/en/camera-mount.html

I found it! Mr Butkus's manual says "37mm"
Have a go: http://www.butkus.org/chinon/voigtlander_pdf/voigtlander_pdf_manuals.htm

 

[edp]

37mm push-on, not screw-on.

 

[Jojje]

I knew it. Sounded too easy...

 

[Loris Medici]

Thanks all, I'm aware about the 37mm push-on. I noticed there are threads in the inner side of the filter ring, I was planning to use a step-up ring (there are shops producing step-up rings for odd sized filter threads) to a more usual filter size (39mm for instance) and use accessories (a lens hood - most importantly!) designed for it.