M39 Leica Thread Mount

[j-becker]

I need a retaining ring for an enlarger lens and the thread is actually an M39 x 26tpi Leica Screw Thread mount. It's a Whitworth thread but I have not been able to locate the actual dimensions for producing it. My edition of the machinery handbook has a microscope thread but not this version. I could probably calculate them assuming it corresponds to the typical thread Whitworth dimensions with nominal 39mm diameter but I though if somebody actually has the dimensions from some source.

 

[Alexander McGilton]

Won't be able to help better than you can Googleing that for documentation.

Why M39 x 26tpi? Did you round up 1.5in and mix with tpi instead of lead or progression per revolution in mm.

You can deduce the lead from the assembly by revolving the parts a set number of revolutions and measuring the progress then dividing to get the lead.

Pitch diameter will be a a challenge to identify. Easy with documentation. But you will otherwise need to use thread wires and the formulas for Whitworth.

 

[Choiliefan]

Beseler Jam Nut

Beseler Jam Nut - The Beseler Jam Nut is a vitally important component used to secure an enlarging lens with a 39mm thread to an enlarger lens board.

www.freestylephoto.com

Just an example.

 

[benmychree]

Amazing what you can find if you know what you are looking for!

 

[toprecyler]

I need a retaining ring for an enlarger lens and the thread is actually an M39 x 26tpi Leica Screw Thread mount. It's a Whitworth thread but I have not been able to locate the actual dimensions for producing it. My edition of the machinery handbook has a microscope thread but not this version. I could probably calculate them assuming it corresponds to the typical thread Whitworth dimensions with nominal 39mm diameter but I though if somebody actually has the dimensions from some source.

I’m curious if it is 26TPI or actually 1mm pitch. There is .0009” difference between the two, so it could be all metric based.

My pitch wire set has instructions on figuring out the pitch diameter, from the nominal dimensions given. I do not have that info with me currently, but the machinery’s handbook should be able to guide you too.


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[woodchucker]

I need a retaining ring for an enlarger lens and the thread is actually an M39 x 26tpi Leica Screw Thread mount. It's a Whitworth thread but I have not been able to locate the actual dimensions for producing it. My edition of the machinery handbook has a microscope thread but not this version. I could probably calculate them assuming it corresponds to the typical thread Whitworth dimensions with nominal 39mm diameter but I though if somebody actually has the dimensions from some source.

how would it be whitworth, whitworth is imperial based, at least from my knowledge of it.
and it would not be 26tpi... you are mixing m39 (metric) with 26 tpi (imperial) and whitworth (imperial).. very doubtful.

 

[Choiliefan]

Leica was the preeminent German camera maker so the thread should be metric.
I have a Leica screwmount lens and a metric thread gage around here somewhere...
According to my gage its a metric 1.0.

 

[Ischgl99]

The OP is 100% correct with his thread specs, it actually is M39 x 26 tpi and a Whitworth thread form. Leitz is the owner of the Leica brand and big into microscopes when the camera mount was developed, microscopes used Whitworth threads at that time, so they likely used that since they were tooled up for it.

@j-becker I couldn’t find any drawings, but this site lists the tolerance class as G/g using ISO designations for internal and external for the L39 thread spec.

Camera mount Threads

 

[j-becker]

Thanks a lot -- I know that I could just buy one from Freestyle or B&H. But I need a couple of them and thought I would give this a spin. After all I have a lathe to dapple with. But all my googling did not turn up the specs yet. These threads are odd ball but have been made in the millions over time. So the specs are sure to be somewhere.

 

[Choiliefan]

Considering the contact area of the lens to jam-nut to lensboard is maybe 1/8" use whatever pitch is most convenient to configure on your lathe.
Metric 1.0 or 26 tpi Whitworth. I'm sure the commercially available part isn't all that exact anyway. Curious what enlarger, lens, etc are you working with? I have an assortment of machines from Leitz Focomat 1C 35mm to Zone VI 5X7 and enlarger lenses from 40mm to 360mm.