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Thread: Lens mounting flanges - measurements and other info

  1. #1
    Ron (Netherlands)'s Avatar
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    Lens mounting flanges - measurements and other info

    Fellow member pgk and I thought it a good idea to start a separate thread on mounting flanges, when we got some ideas about this topic on the ‘Filthy Flange - possibilities’ thread. Main reason is that apart from ourselves we guess that a lot of fellow members have a pile of mounting flanges that not fit precisely or don’t fit at all the lenses we have in our collection. Further it seems quite frustrating that in order to acquire a matching lens mount one has to have one made, which is quite costly, or – at least that is what I did several times – buy one flange or a pile on *bay - also quite costly - and many times afterwards discovering that it doesn’t fit.

    So why this thread: eventually if there is a need, to be able to have an effective/practical – low cost - exchange of lens mounting flanges between fellow members. To do so we would like to agree on:
    a. which measurements and additional info should be provided/needed;
    b. how to take precise measurements of the flanges;
    c. the thread/form to disclose your pile of spare flanges.

    Ad. a. I guess at least the following information should be provided:
    1. material (brass, aluminium, alloy);
    2. outside diameter;
    3. inside diameter;
    4. thread (pitch v/s lead and coarse v/s fine) ;
    5. number of screwholes;
    6. number of visible threads.

    I guess it would be too hard in many cases to determine the thread form, depth and angle.

    Ad. b. Preferably the outside & inside diameter (and if needed the height) should be measured with calipers. Measurements taken with rulers are less accurate (it would therefore help to judge the measurements if info is provided on how measurements are taken).

    Measurement of the thread seems less easy. Screw pitch thread gauges could be of help; there are gauges for Imperial, US and European thread pitches – which could be acquired at low cost. Not sure what the British used before they tried to get to a standard (i.e. I believe Whitworth). The Lens Vademacum has a short section on this topic:
    There are some pointers here:
    (a) Old English lenses up to about 1880 came in fairly fine threaded flanges but many were in 1.5 or 2.0in flanges which were roughly standardized between Ross, Wray, Dallmeyer and Taylor, Taylor and Hobson lenses as well as some others. Thus there is a fair prospect of a match here.
    (b) After 1880, the English makers tended to use 24TPI threads in a rather wide range of sizes so the problem is limited to finding the correct diameter but the thread is probably standard up to quite large sizes.
    (c) Compur and Copal shutters use standard threads and flanges are available from the makers, though care would be needed with older shutters and some old sizes here. Some other lenses have used the same mounting threads but this is not very common.
    (d) But there are many exceptions and here a new flange will have to be made with the trouble and expense this involves.
    (e) There are a wide range of modern fittings used in miniature cameras, where some are easy to match but others are rapidly dropping into obscurity. The makers name on the lens may suggest the mount, but there are pitfalls as with the Canon lens for the Reflecta which fits no other camera satisfactorily.
    It is stressed that the fit should be checked. Dealers can be optimistic as to whether threads match and have a tendency to screw lenses into flanges where the fit is surprisingly poor- half a turn and it jams suggests the wrong pitch rather than the right flange! What is needed is a smooth action and several turns till it screws up tight.


    Further pkg pointed me to the site of skgrimes on how to measure the thread pitch precisely: http://skgrimes.com/library/faq/how-to-measure-threads

    Ad. c. Where to present our piles of spare flanges? I guess as long as we do not put up our flanges for sale or explicit exchange – it would be no problem to have them listed in this thread with all their specifications – having the possibility to have a discussion about them (like the many threads on lenses). However, when one wants them for a sale or exchange, the mounting flange should be listed in the correct “For Sale/For Trade” section.

    If this provides a lot of info, we might take it further to a database on lenses / lensmount specifications.


    More input from fellow members on these topics are welcome

    Last edited by Ron (Netherlands); 23-Aug-2020 at 07:53.
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  2. #2
    Tin Can's Avatar
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    Re: Lens mounting flanges - measurements and other info

    Needs a formal database

    I can't do that
    wear mask or NOT

    is ???

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    Re: Lens mounting flanges - measurements and other info

    That would be ideal and is potentially possible. But in the first instance this would be an information gathering excercise. Without information a database will go nowhere. So if anyone has lens/ring technical data please post and we'll eventually look into what can be done with it.

  4. #4
    Tin Can's Avatar
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    Re: Lens mounting flanges - measurements and other info

    I double space my sentences on purpose

    Purpose being they are readable

    The initial post is way too dense

    I have many flanges, and have had a couple made

    Some lenses can be mounted by ingenuity, even heavy long ones

    Most flanges sell for so little, the effort is doomed, yet a good idea for those with time...
    wear mask or NOT

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  5. #5
    Ron (Netherlands)'s Avatar
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    Re: Lens mounting flanges - measurements and other info

    Just to provide an example of what we are looking for:

    Specifications mounting ring:
    1. material: brass
    2. OD (outside diameter): 2,420"
    3. ID (inside diameter): 1.734"
    4. TPI: 36
    5. 3 screwholes
    6. visible threads (groves): 6

    In short you could specify this ring as: brass 1.734-36

    matching lens: Perken, Son & Rayment Portable Symetrical 5x7 Optimus
    Please note that the lens has a thread diameter of 1.745".

    Another example is my TT&H 8 x 5 R.R. lens, which provides the following specs:
    for the lens: 1.995-24
    for the matching ring: 1.963-24


    Here are some other samples of mounting rings, but these don't fit my lenses:
    flange 1 1.360-34 brass, 3 screwholes
    flange 2 1.445-40 brass, 3 screwholes (truncated thread - UTS/NC?)
    flange 3 37,10mm-M1.0 black painted brass, 4 screwholes
    flange 4 1.495-32 brass, 3 screwholes (truncated thread - UTS/NC?)
    flange 5 1.600-32 brass, 3 screwholes
    flange 6 1.630-36 brass, 3 screwholes
    flange 7 1.665-36 bras, 3 screwholes
    flanges 8 & 9 43,30mm-M1.0 aluminium, 4 screwholes (yes two identical mounting rings)
    flange 10 1.703-36 brass, 3 screwholes
    flange 11 1.960-26 brass, 5 screwholes
    flange 12 2.186-24 black painted brass, 6 screwholes
    flange 13 2.245-30 brass, 3 screwholes
    flange 14 2.465-22 brass, 4 screwholes
    flange 15 55,70mm-M0.75 black painted aluminium, 4 screwholes, inscription: C.P. Goerz - Berlin

    Flanges for small lenses:
    flange 16 1.300-28 brass, 3 screwholes
    flange 17 32,00mm-M0.5 black painted brass, 4 screwholes
    flange 18 30,60mm-M1.0 black painted brass, 3 screwholes
    flange 19 & 20 24,50mm-M1.0 black painted brass, 3 screwholes
    flange 21 0.846-48 chrome-plated brass, 3 screwholes
    Last edited by Ron (Netherlands); 20-Aug-2020 at 02:21. Reason: added some Continental pitches
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    Ron (Netherlands)'s Avatar
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    Re: Lens mounting flanges - measurements and other info

    About British standardisation on mounting flanges I had written down the following but lost the source:
    A standard was agreed upon in 1890 and it seems that Dallmeyer was the driving force behind it. Before a standard came into use, 3 different groups of companies had agreed upon using the same threads:
    1. Ross, Dallmeyer, Ray
    2. Lancaster, Swift
    3. Newton & Co, Reynolds & Co, Suter, TTH, The London Stereoscopic Co.

    The 1890 RPS standard choose 55 dgr Whitworth and further made the following chart:
    Thread pitch / TPI
    1,00 / 24
    1,25 / 24
    1,50 / 24
    1,75 / 24
    2,00 / 24
    3,00 / 24
    3,50 / 12
    4,00 / 12

    Before the standard, mostly used was the 28 TPI until pitch 2,00

    I'm not sure, but it seems that the lens industry (also) made use of BSF, British Standard Fine (as an alternative to British Standard Whitworth; BSW), which has a somewhat different use of thread density, i.e. 16, 18, 20, 22, 28 and 32 TPI. Found no info on how these relate to the different thread pitches.
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    Tin Can's Avatar
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    Re: Lens mounting flanges - measurements and other info

    Restoring Brit motorbikes, I never found a Whitworth Pitch Gauge, yet now common here

    I have 3 sets of 8 sided Thread files I use for thread repair

    Standardization is tough, I found no exact filter match for a modern 1951 Kodak 405 mm, but a miss match works

    My last very large flange I had custom made was affordably made in Thailand to match a 900 mm Jena Tessar bought from there

    Mine is not the one for sale, which is missing the flange

    Your cause is righteous and difficult

    Good luck
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  8. #8
    (Shrek)
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    Re: Lens mounting flanges - measurements and other info

    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.

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    Re: Lens mounting flanges - measurements and other info

    Quote Originally Posted by Tin Can View Post
    Restoring Brit motorbikes, I never found a Whitworth Pitch Gauge, yet now common here
    Its a long time since I had British motorbikes and worked on them but if I remember correctly they used UNC and UNF threads by the 50s and 60s. I think many threads 'approximated' Whitworth threads in terms of pitch angle because it works but even so there are lots of discrepancies. And that's before looking into tolerance and hand matching together with steam or water powered lathes, wear to tools and a myriad of other variables.

    But all that said it would be very useful to have some starting points at least! The RPS 'standardisation' was a bit of a mixed bag I gather as tolerances and subtle differences in production meant that it wasn't as standardised as it was hoped it would be.

    And the problem has been with us for a long time. Photographer Samuel Bourne of Simla, notes in an article that it is useful to have all lenses set up so that they use a common mount - by which I assume he means that his varied lenses (from various manufacturers including Dallmeyer and Grubb) were fitted with some form of adapter to standardise them and make them easier to use. Unfortunately he doesn't describe this further.

  10. #10

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    Re: Lens mounting flanges - measurements and other info

    If only it was that easy. I tend to measure the lens thread as high up and near to the top as possible because lower down threads can be very worn indeed, especially softer brass ones. Even so I think that there has to be some 'judgement' in finalising measurements. But its not impossible.

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