Lens mounting flanges - measurements and other info

[Ron (Netherlands)]

The difficulty if course is that if you take your fancy digital caliper and measure the outside diameter of a lens' thread and the inside diameter of its flange, you will get 2 completely different numbers. Perhaps a section on the math of triangles and thread pitch and angle would help take out some of the guesswork? Even a table or two would do it, such as you will find in machinists' handbooks.

Ie: for a 60 degree 1.25mm thread, subtract "x" from your lens thread measurement to get the thread peak in a flange, or subtract "y" from your flange inside measurement to get the nominal thread diameter of your lens. Decrease that number by a range to account for visibly worn threads, and compare to standard diameters used by different makers.

Yes I do have a big stack of mismatched flanges, and a pile of lenses missing their flange.

In theory this all would be best to strive for. However since - I guess - most of our vintage lenses and mounting rings are quire worn and considering differences in tolerance when they were produced, ruling out the risk of mismatches will be an illusion, and too many variables make it impractical - e.g. most of us won't have instruments measuring a difference between the 55 and 60 dgr angle or the thread pitch. Consider also that most of our vintage lenses & rings are not perfectly round.
However at some points we could strive to more detail, e.g. when I was looking more closely at the threads of my rings, there were two with clearly truncated threads.
Further, looking at the imperial measurements being measured in thousands of an inch, some tolerance between lens and mounting ring should help in successfully matching ring and lens. If you get as you say completely different figures, you won't have a match, however if the differences are in the thousands of that inch (see above example of the Perken lens: difference is 0,0011", providing a perfect match), a match might be possible.
For me it is definitely worth a try.

[pgk]

Further, looking at the imperial measurements being measured in thousands of an inch, some tolerance between lens and mounting ring should help in successfully matching ring and lens

Some makers seem to have worked in fractions of an inch, so a good start point for some early lenses might be matching up the thousandths to fractions, depending on their country of manufacture .....

[Ron (Netherlands)]

Some makers seem to have worked in fractions of an inch, so a good start point for some early lenses might be matching up the thousandths to fractions, depending on their country of manufacture .....

Indeed, at least very good as a sort of double check - I did do so with several of the my rings and because of that changed my opinion about two of them (e.g. the Perken).
I'll have my list now posted in the "For Trade" section too - and if you don't mind, I'll lend your caveat....

[Whir-Click]

This is a worthwhile endeavor. Given the uncertainties in measuring threads, it is helpful to have original dimensions as a reference wherever possible. To that end, I have attached flange thread information from Wollensak lens barrel and shutter engineering drawings.

Caveat: this table is not exhaustive for all Wollensak products. Dimensions are nearly all taken from post-war drawings, so they do not include some older flange sizes referenced in catalogs (such as the 4 11/16” flange for the 16” Vitax), nor flanges for legacy shutters such as the Optimo.

Engineering drawings for the Alphax #4 and #5 flanges are also attached. I will add others if I can find them.

[Ron (Netherlands)]

This is a worthwhile endeavor. Given the uncertainties in measuring threads, it is helpful to have original dimensions as a reference wherever possible. To that end, I have attached flange thread information from Wollensak lens barrel and shutter engineering drawings.

Caveat: this table is not exhaustive for all Wollensak products. Dimensions are nearly all taken from post-war drawings, so they do not include some older flange sizes referenced in catalogs (such as the 4 11/16” flange for the 16” Vitax), nor flanges for legacy shutters such as the Optimo.

Engineering drawings for the Alphax #4 and #5 flanges are also attached. I will add others if I can find them.

Many thanks for your addition Whir-Click, and very interesting info!
Guess we can indeed extend our quest also to shutter mounting (although our title therefore would be a little restricted), why not (I must have some info on German shutters...I'll have a look). Other question is whether we really should include retaining rings which I consider to differ from mounting flanges considering their usage; well some shutters are of course mounted with a flange, others - the many German leaf shutters - are fastened with retaining rings at the back of a board. So I guess we here rather look for the rings with the screwholes, like in your drawings.

[Whir-Click]

I think it’s worth including shutter flanges since, in Wollensak’s case at least, there is considerable interchangeability between lens barrel and shutter flanges. For example, if you’re looking for a flange for a #6 lens barrel, it’s helpful to know that an Alphax#4 shutter flange has the same dimensions.

Other manufacturers may also have some degree of commonality between lens barrel and shutter flange dimensions.

Here is the Ilex shutter flange mounting information (as of 1951):
#00 Precise: 0.953x50
#00 Acme: 1.000x50
#0 : 1.173x40
#1: 1.327x40
#2: 1.606x40
#3: 1.913x40
#4: 2.500x30
#5: 3.232x30

[Ron (Netherlands)]

In my collection of spare mounting rings I found this one which has sort of tightening bots. Anybody knows what it was used for - perhaps an enlarger?

the specs are: 40,10mm-M1.0 black painted brass, 4 screwholes.

Further I have supplemented the above mentioned list in #5 with rings for small lenses (also now in the For Trade section).

Next I'll provide a list of my older vintage lenses with their mounting flanges as a reference for anyone who is in search for a lens or mounting ring.

[pgk]

And FWIW I have an adapter flange for 1.712/28 to 1.912/36 - from ~1883ish and a pencil marking on the back cap which fits the larger male thread is marked Dallmeyer 1/4 plate. So although there was no standardisation of threads by this time, at least some manufacturers/dealers/photographers saw the need for common mounting systems for their lens sets.

[peter brooks]

One day there will be domestic version of the 3D laser scanner, as used to scan archeological sites, volcano craters etc. in remarkable detail. There are already some diy ideas on the internet. 'Male' and 'female' data files could then be produced and shared, and some clever software could analyse a pair and tell you if they fitted together. Oh well, one day...

Presuming that the measuring system used is often inches (for the UK and US in any case) what would be the starting point for making a thread? I made furniture years ago and while I delighted in quarters, eighths and sixteenths of an inch (so much more useful than boring old tenths), it wouldn't make much sense to design something that was (for instance) 2²³/₃₂".

So is a 1.712" female thread for a 1.75" (1³/₄") male thread? And a 1.912" for a 2"? Would the only difference be the pitch and angle of the thread? Knowing the pitch and angle would seem to be key to establishing a match. If the pitch can be accurately measured, and the thread depth also (with a very fine point depth gauge?) then the thread angle can be calculated.

I have a thread gauge and find it far easier to measure external (male) threads, in a similar fashion to the 'mesh two bolts together to see if they are the same thread' scenario. You can see light between, but obviously can't when measuring the internal thread of flanges. Would taking a 'cast' of a section with blutack (putty like stuff for sticking posters etc. to walls) or one of those cold curing modelling clays help?

[Ron (Netherlands)]

Presuming that the measuring system used is often inches (for the UK and US in any case) what would be the starting point for making a thread? I made furniture years ago and while I delighted in quarters, eighths and sixteenths of an inch (so much more useful than boring old tenths), it wouldn't make much sense to design something that was (for instance) 2²³/₃₂".

Guess that is what fellowmember pgk meant when he wrote that "Some makers seem to have worked in fractions of an inch". However until now my experience deviates from that, and I think the optical designers were not hindered by the measurements of the barrel, but only preoccupied with the dimensions of their glasses....therefore the barrel construction had to follow the lens constructions and might have been therefore subordinate. Also the rings that match my (little collection of) vintage British made lenses, don't seem to have been calculated down to fractions of inches.

So is a 1.712" female thread for a 1.75" (1³/₄") male thread? And a 1.912" for a 2"? Would the only difference be the pitch and angle of the thread? Knowing the pitch and angle would seem to be key to establishing a match. If the pitch can be accurately measured, and the thread depth also (with a very fine point depth gauge?) then the thread angle can be calculated.

From my experience (see post #5 for some measurements) each type of barrel/lens seems to have a different 'gap' with its mounting flange, some only 0,0010 and other about 0,0030. At this stage however we cannot provide a definitive answer to this question, much more data would be needed to verify this aspect.

I have a thread gauge and find it far easier to measure external (male) threads, in a similar fashion to the 'mesh two bolts together to see if they are the same thread' scenario. You can see light between, but obviously can't when measuring the internal thread of flanges. Would taking a 'cast' of a section with blutack (putty like stuff for sticking posters etc. to walls) or one of those cold curing modelling clays help?

Could be of help, but I'm not so much into 'silly putty' :-) at least I wouldn't like to smear it into the thread flanges, but others might find it practical.

For a start we only want to ask the data from our fellow members on the basis of which you might rapidly find a possible match between lens and mounting ring, i.e. foremost internal diameter and thread (pitch) per inch. Next, when on the basis of those data two members think they may have a match, they can go ahead and ask for more data....much like a dating site :-)

...but we are of course still awaiting data from other members, there must be huge piles of flanges lying unused in their collections....